Method for producing polydienes and polydiene copolymers with reduced cold flow

ABSTRACT

A method for preparing a coupled polymer, the method comprising the steps of: (i) polymerizing monomer to form a reactive polymer; (ii) reacting the reactive polymer with a polyisocyanate having a functionality of X to form an intermediate polymer product; and (iii) reacting the intermediate polymer product with a polyol having a functionality of Y to form the coupled polymer product, where X+Y≧5.

FIELD OF THE INVENTION

One or more embodiments of the present invention relate to methods forcoupling polydienes or polydiene copolymers. The resultant coupledpolymers of certain embodiments exhibit advantageous cold-flowresistance and improved dynamic properties.

BACKGROUND OF THE INVENTION

Synthetic elastomers having a linear backbone are often employed in themanufacture of tire components, such as sidewalls and treads. It isbelieved that these polymers provide advantageous tensile properties,abrasion resistance, low hysteresis, and fatigue resistance. Forexample, cis-1,4-polydienes have been used in tires. These polymers canbe produced by using lanthanide-based catalyst systems, which results inthe formation of polymers characterized by a linear backbone. Polydieneshaving low or medium cis-1,4-linkage contents and polydiene copolymers,such as random copolymers of butadiene, styrene, and optionallyisoprene, are also often employed in tires. These polymers can generallybe produced by employing anionic initiators, such as n-butyllithium,which yields polymers with a linear backbone.

While synthetic elastomers having a linear backbone demonstrate a numberof advantageous properties, especially for use in tires, these polymersexhibit cold flow due to their linear backbone structures. In otherwords, the polymers with linear backbones flow under their own weight,which causes problems when attempting to transport or store thepolymers. Conventionally, especially with anionically-polymerizedpolymers, the cold flow issues can be alleviated through polymercoupling. Polymer coupling, however, presents several technologicalchallenges. For example, the benefits associated with a reduction incold flow must be balanced with the processability of the polymersduring compounding. Also, the ability to react certain compounds orreagents with a polymer chain, especially the reactive end of a polymerchain, can be unpredictable. Still further, it can be difficult topredict whether any particular coupling agent may have a deleteriousimpact upon one or more of the properties sought from the polymer and/orits use within particular compositions, such as those employed in themanufacture of tire components.

Because there is a need to reduce the cold flow of synthetic elastomerswithout having a deleterious impact on the processability and/or use ofthe polymers, especially in the manufacture of tire components, thereexists a need to develop new coupling agents and methods for couplingpolymers.

SUMMARY OF THE INVENTION

One or more embodiments of the present invention provide a method forpreparing a coupled polymer, the method comprising the steps of: (i)polymerizing monomer to form a reactive polymer; (ii) reacting thereactive polymer with a polyisocyanate having a functionality of X toform an intermediate polymer product; and (iii) reacting theintermediate polymer product with a polyol having a functionality of Yto form the coupled polymer product, where X+Y≧5.

One or more embodiments of the present invention further provide amethod for preparing a coupled polymer, the method comprising the stepsof: (i) polymerizing conjugated diene monomer, and optionally monomercopolymerizable therewith, to form polymer having a reactive chain end;(ii) reacting the reactive chain end of the polymer with apolyisocyanate having a functionality of X to form an intermediatepolymer product; and (iii) reacting the intermediate polymer productwith a polyol having a functionality of Y to form the coupled polymerproduct, where X+Y≧5.

One or more embodiments of the present invention further provide coupledpolymer defined by the formula:

where R¹⁰ is a multivalent organic group deriving from the triol, R¹¹ isa divalent organic group deriving from the diisocyanate, and each R¹² isa polymer chain.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

According to one or more embodiments of the present invention, areactive polymer is prepared by polymerizing conjugated diene monomerand optionally monomer copolymerizable therewith, and this reactivepolymer is then reacted with a polyisocyanate to form an intermediatepolymer product followed by a reaction with a polyol to form a coupledpolymer. In other words, the process of the present invention includes asequential reaction that ultimately produces a coupled polymer. Theresultant coupled polymers can be used in the manufacture of tirecomponents. In one or more embodiments, the resultant coupled polymersexhibit advantageous cold flow resistance and can be used to preparevulcanizates having advantageous dynamic properties.

Polymer Formation

Examples of conjugated diene monomer include 1,3-butadiene, isoprene,1,3-pentadiene, 1,3-hexadiene, 2,3-dimethyl-1,3-butadiene,2-ethyl-1,3-butadiene, 2-methyl-1,3-pentadiene, 3-methyl-1,3-pentadiene,4-methyl-1,3-pentadiene, and 2,4-hexadiene. Mixtures of two or moreconjugated dienes may also be utilized in copolymerization.

Examples of monomer copolymerizable with conjugated diene monomerinclude vinyl-substituted aromatic compounds such as styrene,p-methylstyrene, α-methylstyrene, and vinylnaphthalene.

Coordination Polymerization

In one or more embodiments, the reactive polymer is prepared bycoordination polymerization, wherein monomer is polymerized by using acoordination catalyst system. The key mechanistic features ofcoordination polymerization have been discussed in books (e.g., Kuran,W., Principles of Coordination Polymerization; John Wiley & Sons: NewYork, 2001) and review articles (e.g., Mulhaupt, R., MacromolecularChemistry and Physics 2003, volume 204, pages 289-327). Coordinationcatalysts are believed to initiate the polymerization of monomer by amechanism that involves the coordination or complexation of monomer toan active metal center prior to the insertion of monomer into a growingpolymer chain. An advantageous feature of coordination catalysts istheir ability to provide stereochemical control of polymerizations andthereby produce stereoregular polymers. As is known in the art, thereare numerous methods for creating coordination catalysts, but allmethods eventually generate an active intermediate that is capable ofcoordinating with monomer and inserting monomer into a covalent bondbetween an active metal center and a growing polymer chain. Thecoordination polymerization of conjugated dienes is believed to proceedvia π-allyl complexes as intermediates. Coordination catalysts can beone-, two-, three- or multi-component systems. In one or moreembodiments, a coordination catalyst may be formed by combining a heavymetal compound (e.g., a transition metal compound or alanthanide-containing compound), an alkylating agent (e.g., anorganoaluminum compound), and optionally other co-catalyst components(e.g., a Lewis acid or a Lewis base). In one or more embodiments, theheavy metal compound may be referred to as a coordinating metalcompound.

Various procedures can be used to prepare coordination catalysts. In oneor more embodiments, a coordination catalyst may be formed in situ byseparately adding the catalyst components to the monomer to bepolymerized in either a stepwise or simultaneous manner. In otherembodiments, a coordination catalyst may be preformed. That is, thecatalyst components are pre-mixed outside the polymerization systemeither in the absence of any monomer or in the presence of a smallamount of monomer. The resulting preformed catalyst composition may beaged, if desired, and then added to the monomer that is to bepolymerized.

Useful coordination catalyst systems include lanthanide-based catalystsystems. These catalyst systems may advantageously producecis-1,4-polydienes that, prior to quenching, have reactive chain endsand may be referred to as pseudo-living polymers. While othercoordination catalyst systems may also be employed, lanthanide-basedcatalysts have been found to be particularly advantageous, andtherefore, without limiting the scope of the present invention, will bediscussed in greater detail.

Practice of the present invention is not necessarily limited by theselection of any particular lanthanide-based catalyst system. In one ormore embodiments, the catalyst systems employed include (a) alanthanide-containing compound, (b) an alkylating agent, and (c) ahalogen source. In other embodiments, a compound containing anon-coordinating anion or a non-coordinating anion precursor can beemployed in lieu of a halogen source. In these or other embodiments,other organometallic compounds, Lewis bases, and/or catalyst modifierscan be employed in addition to the ingredients or components set forthabove. For example, in one embodiment, a nickel-containing compound canbe employed as a molecular weight regulator as disclosed in U.S. Pat.No. 6,699,813, which is incorporated herein by reference.

As mentioned above, the lanthanide-based catalyst systems employed inthe present invention can include a lanthanide-containing compound.Lanthanide-containing compounds useful in the present invention arethose compounds that include at least one atom of lanthanum, neodymium,cerium, praseodymium, promethium, samarium, europium, gadolinium,terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, anddidymium. In one embodiment, these compounds can include neodymium,lanthanum, samarium, or didymium. As used herein, the term “didymium”shall denote a commercial mixture of rare-earth elements obtained frommonazite sand. In addition, the lanthanide-containing compounds usefulin the present invention can be in the form of elemental lanthanide.

The lanthanide atom in the lanthanide-containing compounds can be invarious oxidation states including, but not limited to, the 0, +2, +3,and +4 oxidation states. In one embodiment, a trivalentlanthanide-containing compound, where the lanthanide atom is in the +3oxidation state, can be employed. Suitable lanthanide-containingcompounds include, but are not limited to, lanthanide carboxylates,lanthanide organophosphates, lanthanide organophosphonates, lanthanideorganophosphinates, lanthanide carbamates, lanthanide dithiocarbamates,lanthanide xanthates, lanthanide β-diketonates, lanthanide alkoxides oraryloxides, lanthanide halides, lanthanide pseudo-halides, lanthanideoxyhalides, and organolanthanide compounds.

In one or more embodiments, the lanthanide-containing compounds can besoluble in hydrocarbon solvents such as aromatic hydrocarbons, aliphatichydrocarbons, or cycloaliphatic hydrocarbons. Hydrocarbon-insolublelanthanide-containing compounds, however, may also be useful in thepresent invention, as they can be suspended in the polymerization mediumto form the catalytically active species.

For ease of illustration, further discussion of usefullanthanide-containing compounds will focus on neodymium compounds,although those skilled in the art will be able to select similarcompounds that are based upon other lanthanide metals.

Suitable neodymium carboxylates include, but are not limited to,neodymium formate, neodymium acetate, neodymium acrylate, neodymiummethacrylate, neodymium valerate, neodymium gluconate, neodymiumcitrate, neodymium fumarate, neodymium lactate, neodymium maleate,neodymium oxalate, neodymium 2-ethylhexanoate, neodymium neodecanoate(a.k.a., neodymium versatate), neodymium naphthenate, neodymiumstearate, neodymium oleate, neodymium benzoate, and neodymiumpicolinate.

Suitable neodymium organophosphates include, but are not limited to,neodymium dibutyl phosphate, neodymium dipentyl phosphate, neodymiumdihexyl phosphate, neodymium diheptyl phosphate, neodymium dioctylphosphate, neodymium bis(1-methylheptyl) phosphate, neodymiumbis(2-ethylhexyl) phosphate, neodymium didecyl phosphate, neodymiumdidodecyl phosphate, neodymium dioctadecyl phosphate, neodymium dioleylphosphate, neodymium diphenyl phosphate, neodymium bis(p-nonylphenyl)phosphate, neodymium butyl (2-ethylhexyl) phosphate, neodymium(1-methylheptyl) (2-ethylhexyl) phosphate, and neodymium (2-ethylhexyl)(p-nonylphenyl) phosphate.

Suitable neodymium organophosphonates include, but are not limited to,neodymium butyl phosphonate, neodymium pentyl phosphonate, neodymiumhexyl phosphonate, neodymium heptyl phosphonate, neodymium octylphosphonate, neodymium (1-methylheptyl) phosphonate, neodymium(2-ethylhexyl) phosphonate, neodymium decyl phosphonate, neodymiumdodecyl phosphonate, neodymium octadecyl phosphonate, neodymium oleylphosphonate, neodymium phenyl phosphonate, neodymium (p-nonylphenyl)phosphonate, neodymium butyl butylphosphonate, neodymium pentylpentylphosphonate, neodymium hexyl hexylphosphonate, neodymium heptylheptylphosphonate, neodymium octyl octylphosphonate, neodymium(1-methylheptyl) (1-methylheptyl)phosphonate, neodymium (2-ethylhexyl)(2-ethylhexyl)phosphonate, neodymium decyl decylphosphonate, neodymiumdodecyl dodecylphosphonate, neodymium octadecyl octadecylphosphonate,neodymium oleyl oleylphosphonate, neodymium phenyl phenylphosphonate,neodymium (p-nonylphenyl) (p-nonylphenyl)phosphonate, neodymium butyl(2-ethylhexyl)phosphonate, neodymium (2-ethylhexyl)butylphosphonate,neodymium (1-methylheptyl) (2-ethylhexyl)phosphonate, neodymium(2-ethylhexyl) (1-methylheptyl)phosphonate, neodymium (2-ethylhexyl)(p-nonylphenyl)phosphonate, and neodymium (p-nonylphenyl)(2-ethylhexyl)phosphonate.

Suitable neodymium organophosphinates include, but are not limited to,neodymium butylphosphinate, neodymium pentylphosphinate, neodymiumhexylphosphinate, neodymium heptylphosphinate, neodymiumoctylphosphinate, neodymium (1-methylheptyl)phosphinate, neodymium(2-ethylhexyl)phosphinate, neodymium decylphosphinate, neodymiumdodecylphosphinate, neodymium octadecylphosphinate, neodymiumoleylphosphinate, neodymium phenylphosphinate, neodymium(p-nonylphenyephosphinate, neodymium dibutylphosphinate, neodymiumdipentylphosphinate, neodymium dihexylphosphinate, neodymiumdiheptylphosphinate, neodymium dioctylphosphinate, neodymiumbis(1-methylheptyl)phosphinate, neodymium bis(2-ethylhexyl)phosphinate,neodymium didecylphosphinate, neodymium didodecylphosphinate, neodymiumdioctadecylphosphinate, neodymium dioleylphosphinate, neodymiumdiphenylphosphinate, neodymium bis(p-nonylphenyl)phosphinate, neodymiumbutyl (2-ethylhexyl)phosphinate, neodymium(1-methylheptyl)(2-ethylhexyl)phosphinate, and neodymium(2-ethylhexyl)(p-nonylphenyl)phosphinate.

Suitable neodymium carbamates include, but are not limited to, neodymiumdimethylcarbamate, neodymium diethylcarbamate, neodymiumdiisopropylcarbamate, neodymium dibutylcarbamate, and neodymiumdibenzylcarbamate.

Suitable neodymium dithiocarbamates include, but are not limited to,neodymium dimethyldithiocarbamate, neodymium diethyldithiocarbamate,neodymium diisopropyldithiocarbamate, neodymium dibutyldithiocarbamate,and neodymium dibenzyldithiocarbamate.

Suitable neodymium xanthates include, but are not limited to, neodymiummethylxanthate, neodymium ethylxanthate, neodymium isopropylxanthate,neodymium butylxanthate, and neodymium benzylxanthate.

Suitable neodymium β-diketonates include, but are not limited to,neodymium acetylacetonate, neodymium trifluoroacetylacetonate, neodymiumhexafluoroacetylacetonate, neodymium benzoylacetonate, and neodymium2,2,6,6-tetramethyl-3,5-heptanedionate.

Suitable neodymium alkoxides or aryloxides include, but are not limitedto, neodymium methoxide, neodymium ethoxide, neodymium isopropoxide,neodymium 2-ethylhexoxide, neodymium phenoxide, neodymiumnonylphenoxide, and neodymium naphthoxide.

Suitable neodymium halides include, but are not limited to, neodymiumfluoride, neodymium chloride, neodymium bromide, and neodymium iodide.Suitable neodymium pseudo-halides include, but are not limited to,neodymium cyanide, neodymium cyanate, neodymium thiocyanate, neodymiumazide, and neodymium ferrocyanide. Suitable neodymium oxyhalidesinclude, but are not limited to, neodymium oxyfluoride, neodymiumoxychloride, and neodymium oxybromide. A Lewis base, such astetrahydrofuran (“THF”), may be employed as an aid for solubilizing thisclass of neodymium compounds in inert organic solvents. Where lanthanidehalides, lanthanide oxyhalides, or other lanthanide-containing compoundscontaining a halogen atom are employed, the lanthanide-containingcompound may also serve as all or part of the halogen source in theabove-mentioned catalyst system.

As used herein, the term organolanthanide compound refers to anylanthanide-containing compound containing at least one lanthanide-carbonbond. These compounds are predominantly, though not exclusively, thosecontaining cyclopentadienyl (“Cp”), substituted cyclopentadienyl, allyl,and substituted allyl ligands. Suitable organolanthanide compoundsinclude, but are not limited to, Cp₃Ln, Cp₂LnR, Cp₂LnCl, CpLnCl₂,CpLn(cyclooctatetraene), (C₅Me₅)₂LnR, LnR₃, Ln(allyl)₃, andLn(allyl)₂Cl, where Ln represents a lanthanide atom, and R represents ahydrocarbyl group. In one or more embodiments, hydrocarbyl groups usefulin the present invention may contain heteroatoms such as, for example,nitrogen, oxygen, boron, silicon, sulfur, and phosphorus atoms.

As mentioned above, the lanthanide-based catalyst systems employed inthe present invention can include an alkylating agent. In one or moreembodiments, alkylating agents, which may also be referred to ashydrocarbylating agents, include organometallic compounds that cantransfer one or more hydrocarbyl groups to another metal. Typically,these agents include organometallic compounds of electropositive metalssuch as Groups 1, 2, and 3 metals (Groups IA, IIA, and IIIA metals).Alkylating agents useful in the present invention include, but are notlimited to, organoaluminum and organomagnesium compounds. As usedherein, the term organoaluminum compound refers to any aluminum compoundcontaining at least one aluminum-carbon bond. In one or moreembodiments, organoaluminum compounds that are soluble in a hydrocarbonsolvent can be employed. As used herein, the term organomagnesiumcompound refers to any magnesium compound that contains at least onemagnesium-carbon bond. In one or more embodiments, organomagnesiumcompounds that are soluble in a hydrocarbon can be employed. As will bedescribed in more detail below, several species of suitable alkylatingagents can be in the form of a halide. Where the alkylating agentincludes a halogen atom, the alkylating agent may also serve as all orpart of the halogen source in the above-mentioned catalyst system.

In one or more embodiments, organoaluminum compounds that can beutilized include those represented by the general formulaAlR_(n)X_(3-n), where each R independently can be a monovalent organicgroup that is attached to the aluminum atom via a carbon atom, whereeach X independently can be a hydrogen atom, a halogen atom, acarboxylate group, an alkoxide group, or an aryloxide group, and where ncan be an integer in the range of from 1 to 3. In one or moreembodiments, each R independently can be a hydrocarbyl group such as,for example, alkyl, cycloalkyl, substituted cycloalkyl, alkenyl,cycloalkenyl, substituted cycloalkenyl, aryl, substituted aryl, aralkyl,alkaryl, allyl, and alkynyl groups, with each group containing in therange of from 1 carbon atom, or the appropriate minimum number of carbonatoms to form the group, up to about 20 carbon atoms. These hydrocarbylgroups may contain heteroatoms including, but not limited to, nitrogen,oxygen, boron, silicon, sulfur, and phosphorus atoms.

Types of the organoaluminum compounds that are represented by thegeneral formula AlR_(n)X_(3−n) include, but are not limited to,trihydrocarbylaluminum, dihydrocarbylaluminum hydride,hydrocarbylaluminum dihydride, dihydrocarbylaluminum carboxylate,hydrocarbylaluminum bis(carboxylate), dihydrocarbylaluminum alkoxide,hydrocarbylaluminum dialkoxide, dihydrocarbylaluminum halide,hydrocarbylaluminum dihalide, dihydrocarbylaluminum aryloxide, andhydrocarbylaluminum diaryloxide compounds. In one embodiment, thealkylating agent can comprise trihydrocarbylaluminum,dihydrocarbylaluminum hydride, and/or hydrocarbylaluminum dihydridecompounds. In one embodiment, when the alkylating agent includes anorganoaluminum hydride compound, the above-mentioned halogen source canbe provided by a tin halide, as disclosed in U.S. Pat. No. 7,008,899,which is incorporated herein by reference in its entirety.

Suitable trihydrocarbylaluminum compounds include, but are not limitedto, trimethylaluminum, triethylaluminum, triisobutylaluminum,tri-n-propylaluminum, triisopropylaluminum, tri-n-butylaluminum,tri-t-butylaluminum, tri-n-pentylaluminum, trineopentylaluminum,tri-n-hexylaluminum, tri-n-octylaluminum, tris(2-ethylhexyl)aluminum,tricyclohexylaluminum, tris(1-methylcyclopentyl)aluminum,triphenylaluminum, tri-p-tolylaluminum,tris(2,6-dimethylphenyl)aluminum, tribenzylaluminum,diethylphenylaluminum, diethyl-p-tolylaluminum, diethylbenzylaluminum,ethyldiphenylaluminum, ethyldi-p-tolylaluminum, andethyldibenzylaluminum.

Suitable dihydrocarbylaluminum hydride compounds include, but are notlimited to, diethylaluminum hydride, di-n-propylaluminum hydride,diisopropylaluminum hydride, di-n-butylaluminum hydride,diisobutylaluminum hydride, di-n-octylaluminum hydride, diphenylaluminumhydride, di-p-tolylaluminum hydride, dibenzylaluminum hydride,phenylethylaluminum hydride, phenyl-n-propylaluminum hydride,phenylisopropylaluminum hydride, phenyl-n-butylaluminum hydride,phenylisobutylaluminum hydride, phenyl-n-octylaluminum hydride,p-tolylethylaluminum hydride, p-tolyl-n-propylaluminum hydride,p-tolylisopropylaluminum hydride, p-tolyl-n-butylaluminum hydride,p-tolylisobutylaluminum hydride, p-tolyl-n-octylaluminum hydride,benzylethylaluminum hydride, benzyl-n-propylaluminum hydride,benzylisopropylaluminum hydride, benzyl-n-butylaluminum hydride,benzylisobutylaluminum hydride, and benzyl-n-octylaluminum hydride.

Suitable hydrocarbylaluminum dihydrides include, but are not limited to,ethylaluminum dihydride, n-propylaluminum dihydride, isopropylaluminumdihydride, n-butylaluminum dihydride, isobutylaluminum dihydride, andn-octylaluminum dihydride.

Suitable dihydrocarbylaluminum halide compounds include, but are notlimited to, diethylaluminum chloride, di-n-propylaluminum chloride,diisopropylaluminum chloride, di-n-butylaluminum chloride,diisobutylaluminum chloride, di-n-octylaluminum chloride,diphenylaluminum chloride, di-p-tolylaluminum chloride, dibenzylaluminumchloride, phenylethylaluminum chloride, phenyl-n-propylaluminumchloride, phenylisopropylaluminum chloride, phenyl-n-butylaluminumchloride, phenylisobutylaluminum chloride, phenyl-n-octylaluminumchloride, p-tolylethylaluminum chloride, p-tolyl-n-propylaluminumchloride, p-tolylisopropylaluminum chloride, p-tolyl-n-butylaluminumchloride, p-tolylisobutylaluminum chloride, p-tolyl-n-octylaluminumchloride, benzylethylaluminum chloride, benzyl-n-propylaluminumchloride, benzylisopropylaluminum chloride, benzyl-n-butylaluminumchloride, benzylisobutylaluminum chloride, and benzyl-n-octylaluminumchloride.

Suitable hydrocarbylaluminum dihalide compounds include, but are notlimited to, ethylaluminum dichloride, n-propylaluminum dichloride,isopropylaluminum dichloride, n-butylaluminum dichloride,isobutylaluminum dichloride, and n-octylaluminum dichloride.

Other organoaluminum compounds useful as alkylating agents that may berepresented by the general formula AlR_(n)X_(3-n) include, but are notlimited to, dimethylaluminum hexanoate, diethylaluminum octoate,diisobutylaluminum 2-ethylhexanoate, dimethylaluminum neodecanoate,diethylaluminum stearate, diisobutylaluminum oleate, methylaluminumbis(hexanoate), ethylaluminum bis(octoate), isobutylaluminumbis(2-ethylhexanoate), methylaluminum bis(neodecanoate), ethylaluminumbis(stearate), isobutylaluminum bis(oleate), dimethylaluminum methoxide,diethylaluminum methoxide, diisobutylaluminum methoxide,dimethylaluminum ethoxide, diethylaluminum ethoxide, diisobutylaluminumethoxide, dimethylaluminum phenoxide, diethylaluminum phenoxide,diisobutylaluminum phenoxide, methylaluminum dimethoxide, ethylaluminumdimethoxide, isobutylaluminum dimethoxide, methylaluminum diethoxide,ethylaluminum diethoxide, isobutylaluminum diethoxide, methylaluminumdiphenoxide, ethylaluminum diphenoxide, and isobutylaluminumdiphenoxide.

Another class of organoaluminum compounds suitable for use as analkylating agent in the present invention is aluminoxanes. Aluminoxanescan comprise oligomeric linear aluminoxanes, which can be represented bythe general formula:

and oligomeric cyclic aluminoxanes, which can be represented by thegeneral formula:

where x can be an integer in the range of from 1 to about 100, or about10 to about 50; y can be an integer in the range of from 2 to about 100,or about 3 to about 20; and where each R independently can be amonovalent organic group that is attached to the aluminum atom via acarbon atom. In one embodiment, each R independently can be ahydrocarbyl group including, but not limited to, alkyl, cycloalkyl,substituted cycloalkyl, alkenyl, cycloalkenyl, substituted cycloalkenyl,aryl, substituted aryl, aralkyl, alkaryl, allyl, and alkynyl groups,with each group containing in the range of from 1 carbon atom, or theappropriate minimum number of carbon atoms to form the group, up toabout 20 carbon atoms. These hydrocarbyl groups may also containheteroatoms including, but not limited to, nitrogen, oxygen, boron,silicon, sulfur, and phosphorus atoms. It should be noted that thenumber of moles of the aluminoxane as used in this application refers tothe number of moles of the aluminum atoms rather than the number ofmoles of the oligomeric aluminoxane molecules. This convention iscommonly employed in the art of catalyst systems utilizing aluminoxanes.

Aluminoxanes can be prepared by reacting trihydrocarbylaluminumcompounds with water. This reaction can be performed according to knownmethods, such as, for example, (1) a method in which thetrihydrocarbylaluminum compound is dissolved in an organic solvent andthen contacted with water, (2) a method in which thetrihydrocarbylaluminum compound is reacted with water of crystallizationcontained in, for example, metal salts, or water adsorbed in inorganicor organic compounds, or (3) a method in which thetrihydrocarbylaluminum compound is reacted with water in the presence ofthe monomer or monomer solution that is to be polymerized.

Suitable aluminoxane compounds include, but are not limited to,methylaluminoxane (“MAO”), modified methylaluminoxane (“MMAO”),ethylaluminoxane, n-propylaluminoxane, isopropylaluminoxane,butylaluminoxane, isobutylaluminoxane, n-pentylaluminoxane,neopentylaluminoxane, n-hexylaluminoxane, n-octylaluminoxane,2-ethylhexylaluminoxane, cyclohexylaluminoxane,1-methylcyclopentylaluminoxane, phenylaluminoxane, and2,6-dimethylphenylaluminoxane. Modified methylaluminoxane can be formedby substituting about 20 to 80 percent of the methyl groups ofmethylaluminoxane with C₂ to C₁₂ hydrocarbyl groups, preferably withisobutyl groups, by using techniques known to those skilled in the art.

Aluminoxanes can be used alone or in combination with otherorganoaluminum compounds. In one embodiment, methylaluminoxane and atleast one other organoaluminum compound (e.g., AlR_(n)X_(3-n)), such asdiisobutyl aluminum hydride, can be employed in combination. U.S.Publication No. 2008/0182954, which is incorporated herein by referencein its entirety, provides other examples where aluminoxanes andorganoaluminum compounds can be employed in combination.

As mentioned above, alkylating agents useful in the present inventioncan comprise organomagnesium compounds. In one or more embodiments,organomagnesium compounds that can be utilized include those representedby the general formula MgR₂, where each R independently can be amonovalent organic group that is attached to the magnesium atom via acarbon atom. In one or more embodiments, each R independently can be ahydrocarbyl group including, but not limited to, alkyl, cycloalkyl,substituted cycloalkyl, alkenyl, cycloalkenyl, substituted cycloalkenyl,aryl, allyl, substituted aryl, aralkyl, alkaryl, and alkynyl groups,with each group containing in the range of from 1 carbon atom, or theappropriate minimum number of carbon atoms to form the group, up toabout 20 carbon atoms. These hydrocarbyl groups may also containheteroatoms including, but not limited to, nitrogen, oxygen, silicon,sulfur, and phosphorus atoms.

Suitable organomagnesium compounds that may be represented by thegeneral formula MgR₂ include, but are not limited to, diethylmagnesium,di-n-propylmagnesium, diisopropylmagnesium, dibutylmagnesium,dihexylmagnesium, diphenylmagnesium, and dibenzylmagnesium.

Another class of organomagnesium compounds that can be utilized as analkylating agent may be represented by the general formula RMgX, where Rcan be a monovalent organic group that is attached to the magnesium atomvia a carbon atom, and X can be a hydrogen atom, a halogen atom, acarboxylate group, an alkoxide group, or an aryloxide group. Where thealkylating agent is an organomagnesium compound that includes a halogenatom, the organomagnesium compound can serve as both the alkylatingagent and at least a portion of the halogen source in the catalystsystems. In one or more embodiments, R can be a hydrocarbyl groupincluding, but not limited to, alkyl, cycloalkyl, substitutedcycloalkyl, alkenyl, cycloalkenyl, substituted cycloalkenyl, aryl,allyl, substituted aryl, aralkyl, alkaryl, and alkynyl groups, with eachgroup containing in the range of from 1 carbon atom, or the appropriateminimum number of carbon atoms to form the group, up to about 20 carbonatoms. These hydrocarbyl groups may also contain heteroatoms including,but not limited to, nitrogen, oxygen, boron, silicon, sulfur, andphosphorus atoms. In one embodiment, X can be a carboxylate group, analkoxide group, or an aryloxide group, with each group containing in therange of from 1 to about 20 carbon atoms.

Types of organomagnesium compounds that may be represented by thegeneral formula RMgX include, but are not limited to,hydrocarbylmagnesium hydride, hydrocarbylmagnesium halide,hydrocarbylmagnesium carboxylate, hydrocarbylmagnesium alkoxide, andhydrocarbylmagnesium aryloxide.

Suitable organomagnesium compounds that may be represented by thegeneral formula RMgX include, but are not limited to, methylmagnesiumhydride, ethylmagnesium hydride, butylmagnesium hydride, hexylmagnesiumhydride, phenylmagnesium hydride, benzylmagnesium hydride,methylmagnesium chloride, ethylmagnesium chloride, butylmagnesiumchloride, hexylmagnesium chloride, phenylmagnesium chloride,benzylmagnesium chloride, methylmagnesium bromide, ethylmagnesiumbromide, butylmagnesium bromide, hexylmagnesium bromide, phenylmagnesiumbromide, benzylmagnesium bromide, methylmagnesium hexanoate,ethylmagnesium hexanoate, butylmagnesium hexanoate, hexylmagnesiumhexanoate, phenylmagnesium hexanoate, benzylmagnesium hexanoate,methylmagnesium ethoxide, ethylmagnesium ethoxide, butylmagnesiumethoxide, hexylmagnesium ethoxide, phenylmagnesium ethoxide,benzylmagnesium ethoxide, methylmagnesium phenoxide, ethylmagnesiumphenoxide, butylmagnesium phenoxide, hexylmagnesium phenoxide,phenylmagnesium phenoxide, and benzylmagnesium phenoxide.

As mentioned above, the lanthanide-based catalyst systems employed inthe present invention can include a halogen source. As used herein, theterm halogen source refers to any substance including at least onehalogen atom. In one or more embodiments, at least a portion of thehalogen source can be provided by either of the above-describedlanthanide-containing compound and/or the above-described alkylatingagent, when those compounds contain at least one halogen atom. In otherwords, the lanthanide-containing compound can serve as both thelanthanide-containing compound and at least a portion of the halogensource. Similarly, the alkylating agent can serve as both the alkylatingagent and at least a portion of the halogen source.

In another embodiment, at least a portion of the halogen source can bepresent in the catalyst systems in the form of a separate and distincthalogen-containing compound. Various compounds, or mixtures thereof,that contain one or more halogen atoms can be employed as the halogensource. Examples of halogen atoms include, but are not limited to,fluorine, chlorine, bromine, and iodine. A combination of two or morehalogen atoms can also be utilized. Halogen-containing compounds thatare soluble in a hydrocarbon solvent are suitable for use in the presentinvention. Hydrocarbon-insoluble halogen-containing compounds, however,can be suspended in a polymerization system to form the catalyticallyactive species, and are therefore also useful.

Useful types of halogen-containing compounds that can be employedinclude, but are not limited to, elemental halogens, mixed halogens,hydrogen halides, organic halides, inorganic halides, metallic halides,and organometallic halides.

Elemental halogens suitable for use in the present invention include,but are not limited to, fluorine, chlorine, bromine, and iodine. Somespecific examples of suitable mixed halogens include iodinemonochloride, iodine monobromide, iodine trichloride, and iodinepentafluoride.

Hydrogen halides include, but are not limited to, hydrogen fluoride,hydrogen chloride, hydrogen bromide, and hydrogen iodide.

Organic halides include, but are not limited to, t-butyl chloride,t-butyl bromide, allyl chloride, allyl bromide, benzyl chloride, benzylbromide, chloro-di-phenylmethane, bromo-di-phenylmethane,triphenylmethyl chloride, triphenylmethyl bromide, benzylidene chloride,benzylidene bromide, methyltrichlorosilane, phenyltrichlorosilane,dimethyldichlorosilane, diphenyldichlorosilane, trimethylchlorosilane,benzoyl chloride, benzoyl bromide, propionyl chloride, propionylbromide, methyl chloroformate, and methyl bromoformate.

Inorganic halides include, but are not limited to, phosphorustrichloride, phosphorus tribromide, phosphorus pentachloride, phosphorusoxychloride, phosphorus oxybromide, boron trifluoride, borontrichloride, boron tribromide, silicon tetrafluoride, silicontetrachloride, silicon tetrabromide, silicon tetraiodide, arsenictrichloride, arsenic tribromide, arsenic triiodide, seleniumtetrachloride, selenium tetrabromide, tellurium tetrachloride, telluriumtetrabromide, and tellurium tetraiodide.

Metallic halides include, but are not limited to, tin tetrachloride, tintetrabromide, aluminum trichloride, aluminum tribromide, antimonytrichloride, antimony pentachloride, antimony tribromide, aluminumtriiodide, aluminum trifluoride, gallium trichloride, galliumtribromide, gallium triiodide, gallium trifluoride, indium trichloride,indium tribromide, indium triiodide, indium trifluoride, titaniumtetrachloride, titanium tetrabromide, titanium tetraiodide, zincdichloride, zinc dibromide, zinc diiodide, and zinc difluoride.

Organometallic halides include, but are not limited to, dimethylaluminumchloride, diethylaluminum chloride, dimethylaluminum bromide,diethylaluminum bromide, dimethylaluminum fluoride, diethylaluminumfluoride, methylaluminum dichloride, ethylaluminum dichloride,methylaluminum dibromide, ethylaluminum dibromide, methylaluminumdifluoride, ethylaluminum difluoride, methylaluminum sesquichloride,ethylaluminum sesquichloride, isobutylaluminum sesquichloride,methylmagnesium chloride, methylmagnesium bromide, methylmagnesiumiodide, ethylmagnesium chloride, ethylmagnesium bromide, butylmagnesiumchloride, butylmagnesium bromide, phenylmagnesium chloride,phenylmagnesium bromide, benzylmagnesium chloride, trimethyltinchloride, trimethyltin bromide, triethyltin chloride, triethyltinbromide, di-t-butyltin dichloride, di-t-butyltin dibromide, dibutyltindichloride, dibutyltin dibromide, tributyltin chloride, and tributyltinbromide.

In one or more embodiments, the above-described catalyst systems cancomprise a compound containing a non-coordinating anion or anon-coordinating anion precursor. In one or more embodiments, a compoundcontaining a non-coordinating anion, or a non-coordinating anionprecursor can be employed in lieu of the above-described halogen source.A non-coordinating anion is a sterically bulky anion that does not formcoordinate bonds with, for example, the active center of a catalystsystem due to steric hindrance. Non-coordinating anions useful in thepresent invention include, but are not limited to, tetraarylborateanions and fluorinated tetraarylborate anions. Compounds containing anon-coordinating anion can also contain a counter cation, such as acarbonium, ammonium, or phosphonium cation. Exemplary counter cationsinclude, but are not limited to, triarylcarbonium cations andN,N-dialkylanilinium cations. Examples of compounds containing anon-coordinating anion and a counter cation include, but are not limitedto, triphenylcarbonium tetrakis(pentafluorophenyl)borate,N,N-dimethylanilinium tetrakis (pentafluorophenyl)borate,triphenylcarbonium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, andN,N-dimethylanilinium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate.

A non-coordinating anion precursor can also be used in this embodiment.A non-coordinating anion precursor is a compound that is able to form anon-coordinating anion under reaction conditions. Usefulnon-coordinating anion precursors include, but are not limited to,triarylboron compounds, BR₃, where R is a strong electron-withdrawingaryl group, such as a pentafluorophenyl or3,5-bis(trifluoromethyl)phenyl group.

The lanthanide-based catalyst composition used in this invention may beformed by combining or mixing the foregoing catalyst ingredients.Although one or more active catalyst species are believed to result fromthe combination of the lanthanide-based catalyst ingredients, the degreeof interaction or reaction between the various catalyst ingredients orcomponents is not known with any great degree of certainty. Therefore,the term “catalyst composition” has been employed to encompass a simplemixture of the ingredients, a complex of the various ingredients that iscaused by physical or chemical forces of attraction, a chemical reactionproduct of the ingredients, or a combination of the foregoing.

The foregoing lanthanide-based catalyst composition may have highcatalytic activity for polymerizing conjugated dienes intocis-1,4-polydienes over a wide range of catalyst concentrations andcatalyst ingredient ratios. Several factors may impact the optimumconcentration of any one of the catalyst ingredients. For example,because the catalyst ingredients may interact to form an active species,the optimum concentration for any one catalyst ingredient may bedependent upon the concentrations of the other catalyst ingredients.

In one or more embodiments, the molar ratio of the alkylating agent tothe lanthanide-containing compound (alkylating agent/Ln) can be variedfrom about 1:1 to about 1,000:1, in other embodiments from about 2:1 toabout 500:1, and in other embodiments from about 5:1 to about 200:1.

In those embodiments where both an aluminoxane and at least one otherorganoaluminum agent are employed as alkylating agents, the molar ratioof the aluminoxane to the lanthanide-containing compound(aluminoxane/Ln) can be varied from 5:1 to about 1,000:1, in otherembodiments from about 10:1 to about 700:1, and in other embodimentsfrom about 20:1 to about 500:1; and the molar ratio of the at least oneother organoaluminum compound to the lanthanide-containing compound(Al/Ln) can be varied from about 1:1 to about 200:1, in otherembodiments from about 2:1 to about 150:1, and in other embodiments fromabout 5:1 to about 100:1.

The molar ratio of the halogen-containing compound to thelanthanide-containing compound is best described in terms of the ratioof the moles of halogen atoms in the halogen source to the moles oflanthanide atoms in the lanthanide-containing compound (halogen/Ln). Inone or more embodiments, the halogen/Ln molar ratio can be varied fromabout 0.5:1 to about 20:1, in other embodiments from about 1:1 to about10:1, and in other embodiments from about 2:1 to about 6:1.

In yet another embodiment, the molar ratio of the non-coordinating anionor non-coordinating anion precursor to the lanthanide-containingcompound (An/Ln) may be from about 0.5:1 to about 20:1, in otherembodiments from about 0.75:1 to about 10:1, and in other embodimentsfrom about 1:1 to about 6:1.

The lanthanide-based catalyst composition can be formed by variousmethods.

In one embodiment, the lanthanide-based catalyst composition may beformed in situ by adding the catalyst ingredients to a solutioncontaining monomer and solvent, or to bulk monomer, in either a stepwiseor simultaneous manner. In one embodiment, the alkylating agent can beadded first, followed by the lanthanide-containing compound, and thenfollowed by the halogen source or by the compound containing anon-coordinating anion or the non-coordinating anion precursor.

In another embodiment, the lanthanide-based catalyst composition may bepreformed. That is, the catalyst ingredients are pre-mixed outside thepolymerization system either in the absence of any monomer or in thepresence of a small amount of at least one conjugated diene monomer atan appropriate temperature, which may be from about −20° C. to about 80°C. The amount of conjugated diene monomer that may be used forpreforming the catalyst can range from about 1 to about 500 moles, inother embodiments from about 5 to about 250 moles, and in otherembodiments from about 10 to about 100 moles per mole of thelanthanide-containing compound. The resulting catalyst composition maybe aged, if desired, prior to being added to the monomer that is to bepolymerized.

In yet another embodiment, the lanthanide-based catalyst composition maybe formed by using a two-stage procedure. The first stage may involvecombining the alkylating agent with the lanthanide-containing compoundeither in the absence of any monomer or in the presence of a smallamount of at least one conjugated diene monomer at an appropriatetemperature, which may be from about −20° C. to about 80° C. The amountof monomer employed in the first stage may be similar to that set forthabove for preforming the catalyst. In the second stage, the mixtureformed in the first stage and the halogen source, non-coordinatinganion, or non-coordinating anion precursor can be charged in either astepwise or simultaneous manner to the monomer that is to bepolymerized.

Anionic Polymerization

In one or more embodiments, the reactive polymer is prepared by anionicpolymerization, wherein monomer is polymerized by using an anionicinitiator. The key mechanistic features of anionic polymerization havebeen described in books (e.g., Hsieh, H. L.; Quirk, R. P. AnionicPolymerization: Principles and Practical Applications; Marcel Dekker:New York, 1996) and review articles (e.g., Hadjichristidis, N.;Pitsikalis, M.; Pispas, S.; Iatrou, H.; Chem. Rev. 2001, 101(12),3747-3792). Anionic initiators may advantageously produce livingpolymers that, prior to quenching, are capable of reacting withadditional monomers for further chain growth or reacting with certaincoupling agents to give coupled polymers.

The practice of this invention is not limited by the selection of anyparticular anionic initiators. In one or more embodiments, the anionicinitiator employed is a functional initiator that imparts a functionalgroup at the head of the polymer chain (i.e., the location from whichthe polymer chain is started). In particular embodiments, the functionalgroup includes one or more heteroatoms (e.g., nitrogen, oxygen, boron,silicon, sulfur, tin, and phosphorus atoms) or heterocyclic groups. Incertain embodiments, the functional group reduces the 50° C. hysteresisloss of carbon-black filled vulcanizates prepared from polymerscontaining the functional group as compared to similar carbon-blackfilled vulcanizates prepared from polymer that does not include thefunctional group.

Exemplary anionic initiators include organolithium compounds. In one ormore embodiments, organolithium compounds may include heteroatoms. Inthese or other embodiments, organolithium compounds may include one ormore heterocyclic groups.

Types of organolithium compounds include alkyllithium, aryllithiumcompounds, and cycloalkyllithium compounds. Specific examples oforganolithium compounds include ethyllithium, n-propyllithium,isopropyllithium, n-butyllithium, sec-butyllithium, t-butyllithium,n-amyllithium, isoamyllithium, and phenyllithium.

Other anionic initiators include alkylmagnesium halide compounds such asbutylmagnesium bromide and phenylmagnesium bromide. Still other anionicinitiators include organosodium compounds such as phenylsodium and2,4,6-trimethylphenylsodium. Also contemplated are those anionicinitiators that give rise to di-living polymers, wherein both ends of apolymer chain are living. Examples of such initiators include dilithioinitiators such as those prepared by reacting 1,3-diisopropenylbenzenewith sec-butyllithium. These and related difunctional initiators aredisclosed in U.S. Pat. No. 3,652,516, which is incorporated herein byreference. Radical anionic initiators may also be employed, includingthose described in U.S. Pat. No. 5,552,483, which is incorporated hereinby reference.

In particular embodiments, the organolithium compounds include a cyclicamine-containing compound such as lithiohexamethyleneimine. These andrelated useful initiators are disclosed in the U.S. Pat. Nos. 5,332,810,5,329,005, 5,578,542, 5,393,721, 5,698,646, 5,491,230, 5,521,309,5,496,940, 5,574,109, and 5,786,441, which are incorporated herein byreference. In other embodiments, the organolithium compounds includelithiated alkylthioacetals such as 2-lithio-2-methyl-1,3-dithiane. Theseand related useful initiators are disclosed in U.S. Publ. Nos.2006/0030657, 2006/0264590, and 2006/0264589, which are incorporatedherein by reference. In still other embodiments, the organolithiumcompounds include alkoxysilyl-containing initiators, such as lithiatedt-butyldimethylpropoxysilane. These and related useful initiators aredisclosed in U.S. Publ. No. 2006/0241241, which is incorporated hereinby reference.

In one or more embodiments, the anionic initiator employed istrialkyltinlithium compound such as tri-n-butyltinlithium. These andrelated useful initiators are disclosed in U.S. Pat. Nos. 3,426,006 and5,268,439, which are incorporated herein by reference.

When elastomeric copolymers containing conjugated diene monomers andvinyl-substituted aromatic monomers are prepared by anionicpolymerization, the conjugated diene monomers and vinyl-substitutedaromatic monomers may be used at a weight ratio of 95:5 to 50:50, or inother embodiments, 90:10 to 65:35. In order to promote the randomizationof comonomers in copolymerization and to control the microstructure(such as 1,2-linkage of conjugated diene monomer) of the polymer, arandomizer, which is typically a polar coordinator, may be employedalong with the anionic initiator.

Compounds useful as randomizers include those having an oxygen ornitrogen heteroatom and a non-bonded pair of electrons. Exemplary typesof randomizers include linear and cyclic oligomeric oxolanyl alkanes;dialkyl ethers of mono and oligo alkylene glycols (also known as glymeethers); crown ethers; tertiary amines; linear THF oligomers; alkalimetal alkoxides; and alkali metal sulfonates. Linear and cyclicoligomeric oxolanyl alkanes are described in U.S. Pat. No. 4,429,091,which is incorporated herein by reference. Specific examples ofrandomizers include 2,2-bis(2′-tetrahydrofuryl)propane,1,2-dimethoxyethane, N,N,N′,N′-tetramethylethylenediamine (TMEDA),tetrahydrofuran (THF), 1,2-dipiperidylethane, dipiperidylmethane,hexamethylphosphoramide, N,N′-dimethylpiperazine, diazabicyclooctane,dimethyl ether, diethyl ether, tri-n-butylamine, potassium t-amylate,potassium 4-dodecylsulfonate, and mixtures thereof.

The amount of randomizer to be employed may depend on various factorssuch as the desired microstructure of the polymer, the ratio of monomerto comonomer, the polymerization temperature, as well as the nature ofthe specific randomizer employed. In one or more embodiments, the amountof randomizer employed may range between 0.05 and 100 moles per mole ofthe anionic initiator.

The anionic initiator and the randomizer can be introduced to thepolymerization system by various methods. In one or more embodiments,the anionic initiator and the randomizer may be added separately to themonomer to be polymerized in either a stepwise or simultaneous manner.In other embodiments, the anionic initiator and the randomizer may bepre-mixed outside the polymerization system either in the absence of anymonomer or in the presence of a small amount of monomer, and theresulting mixture may be aged, if desired, and then added to the monomerthat is to be polymerized.

In one or more embodiments, regardless of whether a coordinationcatalyst or an anionic initiator is used to prepare the reactivepolymer, a solvent may be employed as a carrier to either dissolve orsuspend the catalyst or initiator in order to facilitate the delivery ofthe catalyst or initiator to the polymerization system. In otherembodiments, monomer can be used as the carrier. In yet otherembodiments, the catalyst or initiator can be used in their neat statewithout any solvent.

In one or more embodiments, suitable solvents include those organiccompounds that will not undergo polymerization or incorporation intopropagating polymer chains during the polymerization of monomer in thepresence of the catalyst or initiator. In one or more embodiments, theseorganic species are liquid at ambient temperature and pressure. In oneor more embodiments, these organic solvents are inert to the catalyst orinitiator. Exemplary organic solvents include hydrocarbons with a low orrelatively low boiling point such as aromatic hydrocarbons, aliphatichydrocarbons, and cycloaliphatic hydrocarbons. Non-limiting examples ofaromatic hydrocarbons include benzene, toluene, xylenes, ethylbenzene,diethylbenzene, and mesitylene. Non-limiting examples of aliphatichydrocarbons include n-pentane, n-hexane, n-heptane, n-octane, n-nonane,n-decane, isopentane, isohexanes, isopentanes, isooctanes,2,2-dimethylbutane, petroleum ether, kerosene, and petroleum spirits.And, non-limiting examples of cycloaliphatic hydrocarbons includecyclopentane, cyclohexane, methylcyclopentane, and methylcyclohexane.Mixtures of the above hydrocarbons may also be used. As is known in theart, aliphatic and cycloaliphatic hydrocarbons may be desirably employedfor environmental reasons. The low-boiling hydrocarbon solvents aretypically separated from the polymer upon completion of thepolymerization.

Other examples of organic solvents include high-boiling hydrocarbons ofhigh molecular weights, including hydrocarbon oils that are commonlyused to oil-extend polymers. Examples of these oils include paraffinicoils, aromatic oils, naphthenic oils, vegetable oils other than castoroils, and low PCA oils including MES, TDAE, SRAE, heavy naphthenic oils.Since these hydrocarbons are non-volatile, they typically do not requireseparation and remain incorporated in the polymer.

The production of the reactive polymer according to this invention canbe accomplished by polymerizing conjugated diene monomer, optionallytogether with monomer copolymerizable with conjugated diene monomer, inthe presence of a catalytically effective amount of the catalyst orinitiator. The introduction of the catalyst or initiator, the conjugateddiene monomer, optionally the comonomer, and any solvent, if employed,forms a polymerization mixture in which the reactive polymer is formed.The amount of the catalyst or initiator to be employed may depend on theinterplay of various factors such as the type of catalyst or initiatoremployed, the purity of the ingredients, the polymerization temperature,the polymerization rate and conversion desired, the molecular weightdesired, and many other factors. Accordingly, a specific catalyst orinitiator amount cannot be definitively set forth except to say thatcatalytically effective amounts of the catalyst or initiator may beused.

In one or more embodiments, the amount of the coordinating metalcompound (e.g., a lanthanide-containing compound) used can be variedfrom about 0.001 to about 2 mmol, in other embodiments from about 0.005to about 1 mmol, and in still other embodiments from about 0.01 to about0.2 mmol per 100 gram of monomer.

In other embodiments, where an anionic initiator (e.g., an alkyllithiumcompound) is employed, the initiator loading may be varied from about0.05 to about 100 mmol, in other embodiments from about 0.1 to about 50mmol, and in still other embodiments from about 0.2 to about 5 mmol per100 gram of monomer.

In one or more embodiments, the polymerization may be carried out in apolymerization system that includes a substantial amount of solvent. Inone embodiment, a solution polymerization system may be employed inwhich both the monomer to be polymerized and the polymer formed aresoluble in the solvent. In another embodiment, a precipitationpolymerization system may be employed by choosing a solvent in which thepolymer formed is insoluble. In both cases, an amount of solvent inaddition to the amount of solvent that may be used in preparing thecatalyst or initiator is usually added to the polymerization system. Theadditional solvent may be the same as or different from the solvent usedin preparing the catalyst or initiator. Exemplary solvents have been setforth above. In one or more embodiments, the solvent content of thepolymerization mixture may be more than 20% by weight, in otherembodiments more than 50% by weight, and in still other embodiments morethan 80% by weight based on the total weight of the polymerizationmixture.

In other embodiments, the polymerization system employed may begenerally considered a bulk polymerization system that includessubstantially no solvent or a minimal amount of solvent. Those skilledin the art will appreciate the benefits of bulk polymerization processes(i.e., processes where monomer acts as the solvent), and therefore thepolymerization system includes less solvent than will deleteriouslyimpact the benefits sought by conducting bulk polymerization. In one ormore embodiments, the solvent content of the polymerization mixture maybe less than about 20% by weight, in other embodiments less than about10% by weight, and in still other embodiments less than about 5% byweight based on the total weight of the polymerization mixture. Inanother embodiment, the polymerization mixture contains no solventsother than those that are inherent to the raw materials employed. Instill another embodiment, the polymerization mixture is substantiallydevoid of solvent, which refers to the absence of that amount of solventthat would otherwise have an appreciable impact on the polymerizationprocess. Polymerization systems that are substantially devoid of solventmay be referred to as including substantially no solvent. In particularembodiments, the polymerization mixture is devoid of solvent.

The polymerization may be conducted in any conventional polymerizationvessels known in the art. In one or more embodiments, solutionpolymerization can be conducted in a conventional stirred-tank reactor.In other embodiments, bulk polymerization can be conducted in aconventional stirred-tank reactor, especially if the monomer conversionis less than about 60%. In still other embodiments, especially where themonomer conversion in a bulk polymerization process is higher than about60%, which typically results in a highly viscous cement, the bulkpolymerization may be conducted in an elongated reactor in which theviscous cement under polymerization is driven to move by piston, orsubstantially by piston. For example, extruders in which the cement ispushed along by a self-cleaning single-screw or double-screw agitatorare suitable for this purpose. Examples of useful bulk polymerizationprocesses are disclosed in U.S. Pat. No. 7,351,776, which isincorporated herein by reference.

In one or more embodiments, all of the ingredients used for thepolymerization can be combined within a single vessel (e.g., aconventional stirred-tank reactor), and all steps of the polymerizationprocess can be conducted within this vessel. In other embodiments, twoor more of the ingredients can be pre-combined in one vessel and thentransferred to another vessel where the polymerization of monomer (or atleast a major portion thereof) may be conducted.

The polymerization can be carried out as a batch process, a continuousprocess, or a semi-continuous process. In the semi-continuous process,the monomer is intermittently charged as needed to replace that monomeralready polymerized. In one or more embodiments, the conditions underwhich the polymerization proceeds may be controlled to maintain thetemperature of the polymerization mixture within a range from about −10°C. to about 200° C., in other embodiments from about 0° C. to about 150°C., and in other embodiments from about 20° C. to about 100° C. In oneor more embodiments, the heat of polymerization may be removed byexternal cooling by a thermally controlled reactor jacket, internalcooling by evaporation and condensation of the monomer through the useof a reflux condenser connected to the reactor, or a combination of thetwo methods. Also, the polymerization conditions may be controlled toconduct the polymerization under a pressure of from about 0.1 atmosphereto about 50 atmospheres, in other embodiments from about 0.5 atmosphereto about 20 atmosphere, and in other embodiments from about 1 atmosphereto about 10 atmospheres. In one or more embodiments, the pressures atwhich the polymerization may be carried out include those that ensurethat the majority of the monomer is in the liquid phase. In these orother embodiments, the polymerization mixture may be maintained underanaerobic conditions.

Coupling with Polyisocyanate and Polyol

Regardless of whether the polymerization is catalyzed or initiated by acoordination catalyst (e.g., a lanthanide-based catalyst) or an anionicinitiator (e.g., an alkyllithium initiator), some or all of theresulting polymer chains may possess reactive chain ends before thepolymerization mixture is quenched. As noted above, the reactive polymerprepared with a coordination catalyst (e.g., a lanthanide-basedcatalyst) may be referred to as a pseudo-living polymer, and thereactive polymer prepared with an anionic initiator (e.g., analkyllithium initiator) may be referred to as a living polymer. In oneor more embodiments, a polymerization mixture including reactive polymermay be referred to as an active polymerization mixture. The percentageof polymer chains possessing a reactive end depends on various factorssuch as the type of catalyst or initiator, the type of monomer, thepurity of the ingredients, the polymerization temperature, the monomerconversion, and many other factors. In one or more embodiments, at leastabout 20% of the polymer chains possess a reactive end, in otherembodiments at least about 50% of the polymer chains possess a reactiveend, and in still other embodiments at least about 80% of the polymerchains possess a reactive end. In any event, the reactive polymer can bereacted with a polyisocyanate to form an intermediate polymer productthat can then be reacted with a polyol to form the coupled polymer ofthis invention.

In one or more embodiments, the total functionality of thepolyisocyanate and the polyol used in preparing the coupled polymers ofthis invention is at least 5. The functionality of the polyisocyanate,which refers to the number of isocyanate groups within thepolyisocyanate molecule, may be represented by the variable X and isgreater than or equal to 2. The functionality of the polyol, whichrefers to the number of isocyanate groups within the polyisocyanatemolecule, may be represented by the variable Y and is greater than orequal to 2. Thus, stated another way, X+Y≧5 with X≧2 and Y≧2.

In one or more embodiments, the polyisocyanates employed in practice ofthe present invention include at least two isocyanato functional groups,which isocyanato functional groups may be defined by the formula —N═C═O.Accordingly, the polyisocyanates may be defined by the formulaR(NCO)_(x), where x is an integer from 2 to 20, in other embodimentsfrom 2 to 10, and in other embodiments from 2 to 3, and where R is amultivalent organic group. In particular embodiments, x is 3.

Examples of multivalent organic groups include divalent organic groups.In one or more embodiments, the divalent organic groups includehydrocarbylene groups or substituted hydrocarbylene groups such as, butnot limited to, alkylene, cycloalkylene, alkenylene, cycloalkenylene,alkynylene, cycloalkynylene, or arylene groups. Substitutedhydrocarbylene groups include hydrocarbylene groups in which one or morehydrogen atoms have been replaced by a substituent such as an alkylgroup. In one or more embodiments, these groups may include from one, orthe appropriate minimum number of carbon atoms to form the group, toabout 20 carbon atoms. These groups may also contain one or moreheteroatoms such as, but not limited to, nitrogen, oxygen, boron,silicon, sulfur, tin, and phosphorus atoms.

In these or other embodiments, the multivalent organic group includes apolymeric species or oligomeric species.

In one or more embodiments, the polyisocyanates may be defined aspolyisocyanato hydrocarbyls, which may include, but are not limited to,diisocyanato hydrocarbyls and triisocyanato hydrocarbyls. In one or moreembodiments, diisocyanato hydrocarbyls include. In one or moreembodiments, triisocyanato hydrocarbyls include triisocyanatoalkyls,triisocyanatocycloalkyls, triisocyantoaryls, triisocyanatoalkenyls, andtriisocyanatoalkynyls.

Exemplary diisocyanato alkyls include 1,8-diisocyanatooctane,1,6-diisocyanatohexane [also called hexamethylene diisocyanate],1,5-diisocyanatohexane, 1,4-diisocyanatohexane, 1,3-diisocyanatohexane,1,2-diisocyanatohexane, 1,5-diisocyanatopentane,1,4-diisocyanatopentane, 1,3-diisocyanatopentane,1,2-diisocyanatopentane, 1,4-diisocyanatobutane, 1,3-diisocyanatobutane,1,2-diisocyanatobutane, 1,3-diisocyanatopropane, 1,2-diisocyantopropane,and 1,3-bis(1-isocyanato-1-methylethyl)benzene.

Exemplary diisocyanato cycloalkyls include5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethyl-cyclohexane [alsocalled isophorone diisocyanate], 1,8-diisocyanatocyclooctane,1,6-diisocyanatocyclohexane, 1,5-diisocyanatocyclohexane,1,4-diisocyanatocyclohexane, 1,3-diisocyanatocyclohexane,1,2-diisocyanatocyclohexane, 1,5-diisocyanatocyclopentane,1,4-diisocyanatocyclopentane, 1,3-diisocyanatocyclopentane,1,2-diisocyanatocyclopentane, and 4,4′-methylenebis(cyclohexylisocyanate).

Exemplary diisocyanato aryls include1-isocyanato-2-[(2-isocyanatophenyl)methyl]-benzene [also called2,4-methylene diphenyl diisocyanate],1-isocyanato-2-[(4-isocyanatophenyl)methyl]-benzene [also called2,4-methylene diphenyl diisocyanate],1-isocyanato-4-[(4-isocyanatophenyl)methyl]-benzene [also called4,4′-methylene diphenyl diisocyanate], 2,4-diisocyanato-1-methyl-benzene[also called tolylene-2,4-diisocyanate],2,5-diisocyanato-1-methyl-benzene [also calledtolylene-2,5-diisocyanate], 2,6-diisocyanato-1-methyl-benzene [alsocalled tolylene-2,6-diisocyanate], 1,4-diisocyanatobenzene [also called1,4-phenylene diisocyanate], 1,3-diisocyanatobenzene [also called1,3-phenylene diisocyanate], 1,2-diisocyanatobenzene [also called1,3-phenylene diisocyanate], 1,5-diisocyantonaphthalene,1,6-diisocyantonaphthalene [also called 1,5-naphthalene diisocyanate],m-xylylene diisocyanate, poly(propylene glycol), tolylene2,4-diisocyanate terminated, poly(ethylene adipate), tolylene2,4-diisocyanate terminated, 2,4,6-trimethyl-1,3-phenylene diisocyanate,4-chloro-6-methyl-1,3-phenylene diisocyanate,4-bromo-6-methyl-1,3-phenylene diisocyanate,3,3′-dimethyl-4,4′-biphenylene diisocyanate, and4,4′-methylenebis(phenyl isocyanate).

Exemplary triisocyanato alkyls include 1,4,8-triisocyanatooctane,1,3,8-triisocyanatooctane, 2,4,8-triisocyanatooctane,1,3,5-triisocyanatooctane, 1,3,6-triisocyanatohexane,1,2,6-triisocyanatohexane, 1,2,5-triisocyanatohexane,1,3,5-triisocyanatohexane, 1,2,3-triisocyanatohexane,1,2,5-triisocyanatopentane, and 1,2,4-triisocyanatopentane.

Exemplary triisocyanato cycloalkyls include1,4,8-triisocyanatocyclooctane, 1,3,8-triisocyanatocyclooctane,2,4,8-triisocyanatocyclooctane, 1,3,5-triisocyanatocyclooctane,1,3,6-triisocyanatocyclohexane, 1,2,6-triisocyanatocyclohexane,1,2,5-triisocyanatocyclohexane, 1,3,5-triisocyanatocyclohexane,1,2,3-triisocyanatocyclohexane, 1,2,5-triisocyanatocyclopentane, and1,2,4-triisocyanatocyclopentane.

An exemplary triisocyanato aryl includes tris(4-isocyanatophenyl)methane[also called triphenylmethane-4,4′,4″-triisocyanate].

In one or more embodiments, mixtures of two or more of the foregoingpolyisocyanates may be employed. In these or other embodiments,oligomers of one or more of the foregoing polyisocyanates may beemployed. For example, mixtures of diphenyl methane diisocyanates (MDI)and oligomers thereof are known in the art as “crude” or polymeric MDIhaving an isocyanate functionality of greater than 2.0.

In one or more embodiments, the polyols employed in practice of thepresent invention include at least two hydroxyl functional groups. Thepolyols may be defined by the formula R(OH)x, where x is an integer from2 to 20, in other embodiments from 2 to 10, and in other embodimentsfrom 2 to 3, and where R is a multivalent organic group.

In one or more embodiments, polyols include diols, triols, and polyolswith four or more hydroxyl groups. Included among these polyols arepolyether polyols and polyester polyols. Useful polyester polyolsinclude phthalic anhydride based polyols and teraphthalic based polyols,as well as blends thereof. Useful polyether polyols include those basedon sucrose and glycerin.

In one or more embodiments, the polyols include diols, which may also bereferred to as hydrocarbyl diols. In one or more embodiments,hydrocarbyl diols include alkyldiols, cycloalkyldiols, aryldiols,alkenyldiols, and akynyldiols. In other embodiments, triols includealkyltriols, cycloalkyltriols, aryltriols, alkenyltriols, andalynyltriols.

Exemplary alkyldiols include 1,2-ethanediol, 1,3-propanediol,1,2-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol,1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 1,2-pentanediol,1,3-pentanediol, 1,4-pentanediol, 1,5-pentanediol, 1,2-hexanediol,1,3-hexanediol, 1,4-hexanediol, 1,5-hexanediol, 1,6-hexanediol,1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, and 1,10-dodecanediol.

Exemplary aryldiols include 1,2-benzenediol (also called catechol),1,3-benezenediol (also called resorcinol), and 1,4-benzenediol (alsocalled hydroquinone).

Exemplary cycloalkyldiols include 1,2-cyclohexanediol,1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclopentanediol,1,3-cyclopentanediol, 1,4-cyclopentanediol, 1,2-cyclooctanediol,1,3-cyclooctanediol, 1,4-cyclooctanediol, 1,5-cyclooctanediol.1,3-cyclododecanediol, and 1,4-cyclododecanediol.

Exemplary alkenyldiols include 2-butene-1,4-diol, 1-pentene-3,4-diol,1-pentene-3,5-diol, 1-pentene-4,5-diol, 2-pentene-1,4-diol,2-pentene-1,5-diol, 1-hexene-3,4-diol, 1-hexene-3,5-diol,1-hexene-3,6-diol, 1-hexene-4,5-diol, 1-hexene-4,6-diol,1-hexene-5,6-diol, 2-hexene-1,4-diol, 2-hexene-1,5-diol,2-hexene-1,6-diol, 3-hexene-1,2-diol, 3-hexene-1,5-diol,3-hexene-1,6-diol, 3-hexene-2,5-diol, 3-hexene-2,6-diol,3-heptene-1,7-diol, 4-octene-1,8-diol, 2-nonene-1,9-diol, and4-dodecene-1,10-diol.

Exemplary alkyltriols include 1,2,3-propanertriol (also called glycerinor glycerol), 1,2,3-butanetriol, 1,2,4-butanetriol, 1,2,3-pentanetriol,1,2,4-pentanetriol, 1,2,5-pentanetriol, 1,3,5-pentanetriol,2,3,4-pentanetriol, 2,3,5-pentanetriol, 1,2,3-hexanetriol,1,2,4-hexanetriol, 1,2,5-hexanetriol, 1,2,6-hexanetriol,2,3,4-hexanetriol, 1,3,7-heptanetriol, 1,4,8-octanetriol,1,3,9-nonanetriol, and 1,5,10-dodecanetriol.

Exemplary aryltriols include 1,2,3-benzenetriol, 1,3,5-benzenetriol, and1,2,4-benzenetriol.

Exemplary cycloalkyltriols include 1,2,3-cyclohexanetriol,1,3,5-cyclohexanetriol, 1,2,4-cyclohexanetriol, 1,2,3-cyclopentanetriol,1,2,4,-cycicopentanetriol, 1,2,3-cyclooctanetriol,1,2,4-cyclooctanetriol, 1,2,5-cyclooctanetriol,1,2,3-cyclododecanetriol, and 1,2,5-cyclododecanetriol.

Exemplary alkenyltriols include 1-pentene-3,4,5-triol,2-pentene-1,4,5-triol, 1-hexene-3,4,5-triol, 1-hexene-3,4,6-triol,1-hexene-3,5,6-triol, 1-hexene-4,5,6-triol, 2-hexene-1,4,5-triol,2-hexene-1,5,6-triol, 2-hexene-4,5,6-triol, 3-heptenetriol-1,2,7,4-octenetriol-1,2,8, 1-nonenetriol-4,5,9, and 4-dodecenetriol-1,3,10.

Amounts of Polyisocyanate and Polyol

The amount of the polyisocyanate that can be added to the polymerizationmixture to yield the intermediate polymer product may depend on variousfactors including the type and amount of catalyst or initiator used tosynthesize the reactive polymer and the desired degree of coupling.

In one or more embodiments, where the reactive polymer is prepared byemploying a lanthanide-based catalyst, the amount of the polyisocyanateemployed to prepare the intermediate polymer product can be describedwith reference to the moles of isocyanate functionality of thepolyisocyanate (i.e., —NCO groups, which may also be referred to asequivalents of isocyanate functionality) and the moles of lanthanidemetal associated with the lanthanide-containing compound (i.e. Ln). Forexample, the molar ratio of the isocyanate functionality to the moles oflanthanide metal (—NCO/Ln) may be from about 1000:1 to about 500:1, inother embodiments from about 500:1 to about 100:1, and in otherembodiments from about 100:1 to about 1:1.

In other embodiments, such as where the reactive polymer is prepared byusing an anionic initiator, the amount of the polyisocyanate employed toprepare the intermediate polymer product can be described with referenceto the moles of isocyanate functionality of the polyisocyanate (i.e.,—NCO groups) and the moles of metal cation (e.g. Li) associated with theinitiator. For example, where an organolithium initiator is employed,the molar ratio of the isocyanate functionality to the moles of lithiumcation (—NCO/Li) may be from about 50:1 to about 10:1, in otherembodiments from about 10:1 to about 5:1, and in other embodiments from5:1 to about 1:1.

The amount of the polyol that can be added to the polymerization mixturecontaining the intermediate polymer product may depend on variousfactors including the type of polyol and/or polyisocyanate and thedesired degree of coupling.

In one or more embodiments, where the reactive polymer is prepared byemploying a lanthanide-based catalyst, the amount of the polyol employedcan be described with reference to the moles of hydroxyl functionalityof the polyol (i.e., —OH, which may also be referred to as theequivalents of the hydroxyl groups) and the moles of lanthanide metalassociated with the lanthanide-containing compound (i.e. Ln). Forexample, the molar ratio of the hydroxyl functionality to the lanthanidemetal (—OH/Ln) may be from about 1000:1 to about 500:1, in otherembodiments from about 500:1 to about 100:1, and in other embodimentsfrom about 100:1 to about 1:1.

In other embodiments, such as where the reactive polymer is prepared byusing an anionic initiator, the amount of the polyol employed can bedescribed with reference to moles of hydroxyl functionality of thepolyol (i.e. —OH) and the moles of metal cation (e.g. Li) associatedwith the initiator. For example, where an organolithium initiator isemployed, the ratio of the functionality of the polyol to the lithiumcation (—OH/Li) may be from about 50:1 to about 10:1, in otherembodiments from about 10:1 to about 5:1, and in other embodiments from5:1 to about 1:1.

Optional Functionalizing Reaction

In one or more embodiments, in addition to the coupling reaction thatinvolves the polyisocyanate and the polyol, a functionalizing agent mayalso be added to the polymerization mixture to functionalize some of thepolymer chains. A mixture of two or more functionalizing agents may alsobe employed. The functionalizing agent may be added to thepolymerization mixture prior to, together with, or after theintroduction of the polyisocyanate and polyol. In one or moreembodiments, the functionalizing agent is added to the polymerizationmixture at least 5 minutes prior to, in other embodiments at least 10minutes prior to, and in other embodiments at least 30 minutes prior tothe introduction of polyisocyanate and polyol. In other embodiments, thefunctionalizing agent is added to the polymerization mixture at least 5minutes after, in other embodiments at least 10 minutes after, and inother embodiments at least 30 minutes after the introduction ofpolyisocyanate and polyol.

In one or more embodiments, functionalizing agents include compounds orreagents that can react with a reactive polymer produced by thisinvention and thereby provide the polymer with a functional group thatis distinct from a propagating chain that has not been reacted with thefunctionalizing agent. The functional group may be reactive orinteractive with other polymer chains (propagating and/ornon-propagating) or with other constituents such as reinforcing fillers(e.g. carbon black) that may be combined with the polymer. In one ormore embodiments, the reaction between the functionalizing agent and thereactive polymer proceeds via an addition or substitution reaction.

Useful functionalizing agents may include compounds that simply providea functional group at the end of a polymer chain. In one or moreembodiments, functionalizing agents include compounds that will add orimpart a heteroatom to the polymer chain. In particular embodiments,functionalizing agents include those compounds that will impart afunctional group to the polymer chain to form a functionalized polymerthat reduces the 50° C. hysteresis loss of a carbon-black filledvulcanizates prepared from the functionalized polymer as compared tosimilar carbon-black filled vulcanizates prepared fromnon-functionalized polymer. In one or more embodiments, this reductionin hysteresis loss is at least 5%, in other embodiments at least 10%,and in other embodiments at least 15%.

Co-Coupling Reagents

In other embodiments, an additional coupling agent may be used incombination with the polyisocyanate and polyol. These compounds, whichmay be referred to as co-coupling agents, may join two or more polymerchains together to form a single macromolecule. Because certainfunctionalizing agents may serve to couple polymer chains in addition toproviding the polymer chain with a useful functionality, the co-couplingagents may simply be referred to as functionalizing agents herein.

In one or more embodiments, suitable functionalizing agents includethose compounds that contain groups that may react with the reactivepolymers produced in accordance with this invention. Exemplaryfunctionalizing agents include ketones, quinones, aldehydes, amides,esters, isocyanates, isothiocyanates, epoxides, imines, aminoketones,aminothioketones, and acid anhydrides. Examples of these compounds aredisclosed in U.S. Pat. Nos. 4,906,706, 4,990,573, 5,064,910, 5,567,784,5,844,050, 6,838,526, 6,977,281, and 6,992,147; U.S. Pat. PublicationNos. 2006/0004131 A1, 2006/0025539 A1, 2006/0030677 A1, and 2004/0147694A1; Japanese Patent Application Nos. 05-051406A, 05-059103A, 10-306113A,and 11-035633A; which are incorporated herein by reference. Otherexamples of functionalizing agents include azine compounds as describedin U.S. Ser. No. 11/640,711, hydrobenzamide compounds as disclosed inU.S. Ser. No. 11/710,713, nitro compounds as disclosed in U.S. Ser. No.11/710,845, and protected oxime compounds as disclosed in U.S. Ser. No.60/875,484, all of which are incorporated herein by reference.

In particular embodiments, the functionalizing agents employed may bemetal halides, metalloid halides, alkoxysilanes, metal carboxylates,hydrocarbylmetal carboxylates, hydrocarbylmetal ester-carboxylates, andmetal alkoxides.

Exemplary metal halide compounds include tin tetrachloride, tintetrabromide, tin tetraiodide, n-butyltin trichloride, phenyltintrichloride, di-n-butyltin dichloride, diphenyltin dichloride,tri-n-butyltin chloride, triphenyltin chloride, germanium tetrachloride,germanium tetrabromide, germanium tetraiodide, n-butylgermaniumtrichloride, di-n-butylgermanium dichloride, and tri-n-butylgermaniumchloride.

Exemplary metalloid halide compounds include silicon tetrachloride,silicon tetrabromide, silicon tetraiodide, methyltrichlorosilane,phenyltrichlorosilane, dimethyldichlorosilane, diphenyldichlorosilane,boron trichloride, boron tribromide, boron triiodide, phosphoroustrichloride, phosphorous tribromide, and phosphorus triiodide.

In one or more embodiments, the alkoxysilanes may include at least onegroup selected from the group consisting of an epoxy group and anisocyanate group.

Exemplary alkoxysilane compounds including an epoxy group include(3-glycidyloxypropyl)trimethoxysilane,(3-glycidyloxypropyl)triethoxysilane,(3-glycidyloxypropyl)triphenoxysilane,(3-glycidyloxypropyl)methyldimethoxysilane,(3-glycidyloxypropyl)methyldiethoxysilane,(3-glycidyloxypropyl)methyldiphenoxysilane,[2-(3,4-epoxycyclohexyl)ethyl]trimethoxysilane, and[2-(3,4-epoxycyclohexyl)ethyl]triethoxysilane.

Exemplary alkoxysilane compounds including an isocyanate group include(3-isocyanatopropyl)trimethoxysilane,(3-isocyanatopropyl)triethoxysilane,(3-isocyanatopropyl)triphenoxysilane,(3-isocyanatopropyl)methyldimethoxysilane,(3-isocyanatopropyl)methyldiethoxysilane(3-isocyanatopropyl)methyldiphenoxysilane, and(isocyanatomethyl)methyldimethoxysilane.

Exemplary metal carboxylate compounds include tin tetraacetate, tinbis(2-ethylhexanaote), and tin bis(neodecanoate).

Exemplary hydrocarbylmetal carboxylate compounds include triphenyltin2-ethylhexanoate, tri-n-butyltin 2-ethylhexanoate, tri-n-butyltinneodecanoate, triisobutyltin 2-ethylhexanoate, diphenyltinbis(2-ethylhexanoate), di-n-butyltin bis (2-ethylhexanoate),di-n-butyltin bis(neodecanoate), phenyltin tris(2-ethylhexanoate), andn-butyltin tris(2-ethylhexanoate).

Exemplary hydrocarbylmetal ester-carboxylate compounds includedi-n-butyltin bis(n-octylmaleate), di-n-octyltin bis(n-octylmaleate),diphenyltin bis(n-octylmaleate), di-n-butyltin bis(2-ethylhexylmaleate),di-n-octyltin bis(2-ethylhexylmaleate), and diphenyltinbis(2-ethylhexylmaleate).

Exemplary metal alkoxide compounds include dimethoxytin, diethoxytin,tetraethoxytin, tetra-n-propoxytin, tetraisopropoxytin,tetra-n-butoxytin, tetraisobutoxytin, tetra-t-butoxytin, andtetraphenoxytin.

The amount of the functionalizing agent that can be added to thepolymerization mixture may depend on various factors including the typeand amount of catalyst or initiator used to synthesize the reactivepolymer and the desired degree of functionalization. In one or moreembodiments, where the reactive polymer is prepared by employing alanthanide-based catalyst, the amount of the functionalizing agentemployed can be described with reference to the lanthanide metal of thelanthanide-containing compound. For example, the molar ratio of thefunctionalizing agent to the lanthanide metal may be from about 1:1 toabout 200:1, in other embodiments from about 5:1 to about 150:1, and inother embodiments from about 10:1 to about 100:1.

In other embodiments, such as where the reactive polymer is prepared byusing an anionic initiator, the amount of the functionalizing agentemployed can be described with reference to the amount of metal cationassociated with the initiator. For example, where an organolithiuminitiator is employed, the molar ratio of the functionalizing agent tothe lithium cation may be from about 0.3:1 to about 2:1, in otherembodiments from about 0.6:1 to about 1.5:1, and in other embodimentsfrom 0.8:1 to about 1.2:1.

The amount of the functionalizing agent employed can also be describedwith reference to the polyisocyanate and polyol. In one or moreembodiments, the molar ratio of the functionalizing agent to thepolyisocyanate and polyol may be from about 0.1:1 to about 10:1, inother embodiments from about 0.2:1 to about 5:1, and in otherembodiments from about 0.5:1 to about 2:1.

Coupling Reaction

In one or more embodiments, the polyisocyanate and polyol (andoptionally the functionalizing agent) may be introduced to thepolymerization mixture at a location (e.g., within a vessel) where thepolymerization has been conducted. In other embodiments, thepolyisocyanate and polyol may be introduced to the polymerizationmixture at a location that is distinct from where the polymerization hastaken place. For example, the polyisocyanate and polyol may beintroduced to the polymerization mixture in downstream vessels includingdownstream reactors or tanks, in-line reactors or mixers, extruders, ordevolatilizers. And, the polyisocyanate and the polyol can be introducedat separate locations.

In one or more embodiments, the polyisocyanate (and optionally thefunctionalizing agent) can be introduced to the polymerization mixtureafter a desired monomer conversion is achieved but before thepolymerization mixture is quenched by a quenching agent. In one or moreembodiments, the introduction of the polyisocyanate to the reactivepolymer may take place within 30 minutes, in other embodiments within 5minutes, and in other embodiments within one minute after the peakpolymerization temperature is reached. In one or more embodiments, theintroduction of the polyisocyanate to the reactive polymer can occuronce the peak polymerization temperature is reached. In otherembodiments, the introduction of the polyisocyanate to the reactivepolymer can occur after the reactive polymer has been stored. In one ormore embodiments, the storage of the reactive polymer occurs at roomtemperature or below room temperature under an inert atmosphere.

In one or more embodiments, the introduction of the polyisocyanate tothe reactive polymer may take place at a temperature from about 10° C.to about 150° C., and in other embodiments from about 20° C. to about100° C. The time required for completing the reaction between thepolyisocyanate and the reactive polymer depends on various factors suchas the type and amount of the catalyst or initiator used to prepare thereactive polymer, the type and amount of the polyisocyanate, as well asthe temperature at which the reaction is conducted. In one or moreembodiments, the reaction between the polyisocyanate and the reactivepolymer can be conducted for about 1 to 60 minutes, in other embodimentsfor about 1 to 30 minutes, and in other embodiments for about 1 to 5minutes.

Once a desired amount of time is provided for the polyisocyanate toreact with the reactive polymer, the polyol can be introduced to thepolymerization mixture, which now includes the intermediate polymerproduct. As those skilled in the art will appreciate, the polyol isadded prior to the introduction of a quenching agent other than thepolyol intended for use in the sequential coupling reaction.

In one or more embodiments, the introduction of the polyol to thepolymerization mixture takes place after 300 minutes, in otherembodiments after 150 minutes, and in other embodiments after 60 minutesfrom the introduction of the polyisocyanate to the polymerizationmixture. In these or other embodiments, the introduction of the polyolto the polymerization mixture takes place within 30 minutes, in otherembodiments within 15 minutes, and in other embodiments within 5 minutesfrom the introduction of the polyisocyanate to the polymerizationmixture.

In one or more embodiments, the introduction of the polyol to thepolymerization mixture containing the intermediate polymer product maytake place at a temperature from about 10° C. to about 150° C., and inother embodiments from about 20° C. to about 100° C. The time requiredfor completing the reaction between the polyol and the intermediatepolymer product depends on various factors such as the type and amountof the polyisocyanate and polyol, as well as the temperature at whichthe reaction is conducted. In one or more embodiments, the reactionbetween the polyol and the intermediate polymer product can be conductedfor about 300 to 60 minutes, in other embodiments for about 60 to 30minutes, and in other embodiments for about 30 to 1 minutes.

Quenching

In one or more embodiments, after the reaction between the reactivepolymer and the polyisocyanate and polyol (and optionally thefunctionalizing agent) has been accomplished or completed, a quenchingagent can be optionally added to the polymerization mixture in order toprotonate and/or inactivate any residual reactive polymer chains, and/orinactivate the catalyst or catalyst components. The quenching agent mayinclude a protic compound, which includes, but is not limited to, analcohol, a carboxylic acid, an inorganic acid, water, or a mixturethereof. In particular embodiments, the process is devoid of using aquenching agent other than the polyol used in the coupling reaction. Anantioxidant such as 2,6-di-tert-butyl-4-methylphenol may be added alongwith, before, or after the addition of the quenching agent. The amountof the antioxidant employed may be in the range of 0.2% to 1% by weightof the polymer product. Additionally, the polymer product can be oilextended by adding an oil to the polymer, which may be in the form of apolymer cement or polymer dissolved or suspended in monomer. Practice ofthe present invention does not limit the amount of oil that may beadded, and therefore conventional amounts may be added (e.g., 5-50 phr).Useful oils or extenders that may be employed include, but are notlimited to, aromatic oils, paraffinic oils, naphthenic oils, vegetableoils other than castor oils, low PCA oils including MES, TDAE, and SRAE,and heavy naphthenic oils.

Polymer Recovery

Once the coupling reaction has been completed by providing a desiredtime for the polyol to react with the intermediate polymer product,and/or any subsequent additions (e.g., oil) are introduced to thepolymerization mixture, the various constituents of the polymerizationmixture may be recovered. In one or more embodiments, the unreactedmonomer can be recovered from the polymerization mixture. For example,the monomer can be distilled from the polymerization mixture by usingtechniques known in the art. In one or more embodiments, a devolatilizermay be employed to remove the monomer from the polymerization mixture.Once the monomer has been removed from the polymerization mixture, themonomer may be purified, stored, and/or recycled back to thepolymerization process.

The polymer product may be recovered from the polymerization mixture byusing techniques known in the art. In one or more embodiments,desolventization and drying techniques may be used. For instance, thepolymer can be recovered by passing the polymerization mixture through aheated screw apparatus, such as a desolventizing extruder, in which thevolatile substances are removed by evaporation at appropriatetemperatures (e.g., about 100° C. to about 170° C.) and underatmospheric or sub-atmospheric pressure. This treatment serves to removeunreacted monomer as well as any low-boiling solvent. Alternatively, thepolymer can also be recovered by subjecting the polymerization mixtureto steam desolventization, followed by drying the resulting polymercrumbs in a hot air tunnel. The polymer can also be recovered bydirectly drying the polymerization mixture on a drum dryer.

Polymer Product

The reactive polymer and the polyisocyanate (and optionally thefunctionalizing agent) are believed to react to produce the intermediatepolymer product, which is believed to include at least one isocyanateend functionality. Specifically, it is believed that the living polymeradds to a first isocyanate functionality of the polyisocyanate via anucleophilic addition reaction, thereby imparting the residue of thepolyisocyanate to the end of the polymeric chain. The residue of thepolyisocyanate includes at least one isocyanate functionality that cansubsequently react with the polyol. Thus, the introduction of the polyolto the polymerization mixture including the intermediate polymer productis believed to lead to a reaction with at least one isocyanatefunctionality to produce the coupled polymer product. Specifically, thepolyol is believed to react with the isocyanate in a polyurethane-typereaction that produces a carbamate linkage between the polyisocyanateresidue and the polyol residue.

Nonetheless, the exact chemical structure of the coupled polymerproduced in every embodiment is not known with any great degree ofcertainty, particularly as the structure relates to the residue impartedto the polymer chain end by the polyisocyanate and/or polyol andoptionally the functionalizing agent. Indeed, it is speculated that thestructure of the coupled polymer may depend upon various factors such asthe conditions employed to prepare the reactive polymer (e.g., the typeand amount of the catalyst or initiator) and the conditions employed toreact the polyisocyanate and/or polyol (and optionally thefunctionalizing agent) with the reactive polymer (e.g., the types andamounts of the polyisocyanate and polyol and the functionalizing agent).

In one or more embodiments, particularly where a diisocyanate isemployed to form the intermediate polymer product, and a triol isemployed to couple the intermediate polymer product, one of the coupledpolymers may be defined by the formula

where R¹⁰ is a multivalent organic group deriving from the triol, R¹¹ isa divalent organic group deriving from the diisocyanate, and each R¹² isa polymer chain.

In one or more embodiments, the coupled polymers prepared according tothis invention may contain unsaturation. In these or other embodiments,the coupled polymers are vulcanizable. In one or more embodiments, thecoupled polymers can have a glass transition temperature (T_(g)) that isless than 0° C., in other embodiments less than −20° C., and in otherembodiments less than −30° C. In one embodiment, these polymers mayexhibit a single glass transition temperature. In particularembodiments, the polymers may be hydrogenated or partially hydrogenated.

In one or more embodiments, the coupled polymers of this invention maybe cis-1,4-polydienes having a cis-1,4-linkage content that is greaterthan 60%, in other embodiments greater than about 75%, in otherembodiments greater than about 90%, and in other embodiments greaterthan about 95%, where the percentages are based upon the number of dienemer units adopting the cis-1,4 linkage versus the total number of dienemer units. Also, these polymers may have a 1,2-linkage content that isless than about 7%, in other embodiments less than 5%, in otherembodiments less than 2%, and in other embodiments less than 1%, wherethe percentages are based upon the number of diene mer units adoptingthe 1,2-linkage versus the total number of diene mer units. The balanceof the diene mer units may adopt the trans-1,4-linkage. The cis-1,4-,1,2-, and trans-1,4-linkage contents can be determined by infraredspectroscopy. The number average molecular weight (M_(n)) of thesepolymers may be from about 1,000 to about 1,000,000, in otherembodiments from about 5,000 to about 200,000, in other embodiments fromabout 25,000 to about 150,000, and in other embodiments from about50,000 to about 120,000, as determined by using gel permeationchromatography (GPC) calibrated with polystyrene standards andMark-Houwink constants for the polymer in question. The molecular weightdistribution or polydispersity (M_(w)/M_(n)) of these polymers may befrom about 1.5 to about 5.0, and in other embodiments from about 2.0 toabout 4.0.

In one or more embodiments, the coupled polymers of this invention maybe cis-1,4-polydienes having a cis-1,4-linkage content that is greaterthan 60%, in other embodiments greater than about 75%, in otherembodiments greater than about 90%, and in other embodiments greaterthan about 95%, where the percentages are based upon the number of dienemer units adopting the cis-1,4 linkage versus the total number of dienemer units. Also, these polymers may have a 1,2-linkage content that isless than about 7%, in other embodiments less than 5%, in otherembodiments less than 2%, and in other embodiments less than 1%, wherethe percentages are based upon the number of diene mer units adoptingthe 1,2-linkage versus the total number of diene mer units. The balanceof the diene mer units may adopt the trans-1,4-linkage. The cis-1,4-,1,2-, and trans-1,4-linkage contents can be determined by infraredspectroscopy. The number average molecular weight (M_(n)) of thesepolymers may be from about 1,000 to about 1,000,000, in otherembodiments from about 5,000 to about 200,000, in other embodiments fromabout 25,000 to about 150,000, and in other embodiments from about50,000 to about 120,000, as determined by using gel permeationchromatography (GPC) calibrated with polystyrene standards andMark-Houwink constants for the polymer in question. The polydispersity(M_(w)/M_(n)) of these polymers may be from about 1.5 to about 5.0, andin other embodiments from about 2.0 to about 4.0.

In one or more embodiments, the coupled polymers of this invention maybe polydienes or polydiene copolymers (e.g. copolymers of dienes withvinyl aromatic monomer) having medium or low cis-1,4-linkage contents.These polymers, which can be prepared by anionic polymerizationtechniques, can have a cis-1,4-linkage content of from about 10% to 60%,in other embodiments from about 15% to 55%, and in other embodimentsfrom about 20% to about 50%. These polydienes may also have a1,2-linkage content from about 10% to about 90%, in other embodimentsfrom about 10% to about 60%, in other embodiments from about 15% toabout 50%, and in other embodiments from about 20% to about 45%. Inparticular embodiments, where the polydienes are prepared by employing afunctional anionic initiator, the head of the polymer chains include afunctional group that is the residue of the functional initiator.

In particular embodiments, the coupled polymers of this invention arecopolymers of 1,3-butadiene, styrene, and optionally isoprene. These mayinclude random copolymers and block copolymers. In one or moreembodiments, the random polydiene copolymers may include from about 10to about 50% by weight, in other embodiments from about 15 to about 40%by weight, and in other embodiments from about 20 to about 30% by weightunits deriving from styrene, with the balance including units derivingfrom conjugated diene monomer, such as 1,3-butadiene, having low ormedium cis content as described above.

Industrial Applicability

Advantageously, the coupled polymers of this invention may exhibitimproved cold-flow resistance. The coupled polymers are particularlyuseful in preparing rubber compositions that can be used to manufacturetire components. Rubber compounding techniques and the additivesemployed therein are generally disclosed in The Compounding andVulcanization of Rubber, in Rubber Technology (2^(nd) Ed. 1973).

The rubber compositions can be prepared by using the coupled polymersalone or together with other elastomers (i.e., polymers that can bevulcanized to form compositions possessing rubbery or elastomericproperties). Other elastomers that may be used include natural andsynthetic rubbers. The synthetic rubbers typically derive from thepolymerization of conjugated diene monomers, the copolymerization ofconjugated diene monomers with other monomers such as vinyl-substitutedaromatic monomers, or the copolymerization of ethylene with one or moreα-olefins and optionally one or more diene monomers.

Exemplary elastomers include natural rubber, synthetic polyisoprene,polybutadiene, polyisobutylene-co-isoprene, neoprene,poly(ethylene-co-propylene), poly(styrene-co-butadiene),poly(styrene-co-isoprene), poly(styrene-co-isoprene-co-butadiene),poly(isoprene-co-butadiene), poly(ethylene-co-propylene-co-diene),polysulfide rubber, acrylic rubber, urethane rubber, silicone rubber,epichlorohydrin rubber, and mixtures thereof. These elastomers can havea myriad of macromolecular structures including linear, branched, andstar-shaped structures.

The rubber compositions may include fillers such as inorganic andorganic fillers. Examples of organic fillers include carbon black andstarch. Examples of inorganic fillers include silica, aluminumhydroxide, magnesium hydroxide, mica, talc (hydrated magnesiumsilicate), and clays (hydrated aluminum silicates). Carbon blacks andsilicas are the most common fillers used in manufacturing tires. Incertain embodiments, a mixture of different fillers may beadvantageously employed.

In one or more embodiments, carbon blacks include furnace blacks,channel blacks, and lamp blacks. More specific examples of carbon blacksinclude super abrasion furnace blacks, intermediate super abrasionfurnace blacks, high abrasion furnace blacks, fast extrusion furnaceblacks, fine furnace blacks, semi-reinforcing furnace blacks, mediumprocessing channel blacks, hard processing channel blacks, conductingchannel blacks, and acetylene blacks.

In particular embodiments, the carbon blacks may have a surface area(EMSA) of at least 20 m²/g and in other embodiments at least 35 m²/g;surface area values can be determined by ASTM D-1765 using thecetyltrimethylammonium bromide (CTAB) technique. The carbon blacks maybe in a pelletized form or an unpelletized flocculent form. Thepreferred form of carbon black may depend upon the type of mixingequipment used to mix the rubber compound.

The amount of carbon black employed in the rubber compositions can be upto about 50 parts by weight per 100 parts by weight of rubber (phr),with about 5 to about 40 phr being typical.

Some commercially available silicas which may be used include Hi-Sil™215, Hi-Sil™ 233, and Hi-Sil™ 190 (PPG Industries, Inc.; Pittsburgh,Pa.). Other suppliers of commercially available silica include GraceDavison (Baltimore, Md.), Degussa Corp. (Parsippany, N.J.), RhodiaSilica Systems (Cranbury, N.J.), and J.M. Huber Corp. (Edison, N.J.).

In one or more embodiments, silicas may be characterized by theirsurface areas, which give a measure of their reinforcing character. TheBrunauer, Emmet and Teller (“BET”) method (described in J. Am. Chem.Soc., vol. 60, p. 309 et seq.) is a recognized method for determiningthe surface area. The BET surface area of silica is generally less than450 m²/g. Useful ranges of surface area include from about 32 to about400 m²/g, about 100 to about 250 m²/g, and about 150 to about 220 m²/g.

The pH's of the silicas are generally from about 5 to about 7 orslightly over 7, or in other embodiments from about 5.5 to about 6.8.

In one or more embodiments, where silica is employed as a filler (aloneor in combination with other fillers), a silica coupling agent and/or asilica shielding agent may be added to the rubber compositions duringmixing in order to enhance the interaction of silica with theelastomers. Useful silica coupling agents and silica shielding agentsare disclosed in U.S. Pat. Nos. 3,842,111, 3,873,489, 3,978,103,3,997,581, 4,002,594, 5,580,919, 5,583,245, 5,663,396, 5,674,932,5,684,171, 5,684,172 5,696,197, 6,608,145, 6,667,362, 6,579,949,6,590,017, 6,525,118, 6,342,552, and 6,683,135, which are incorporatedherein by reference.

The amount of silica employed in the rubber compositions can be fromabout 1 to about 100 phr or in other embodiments from about 5 to about80 phr. The useful upper range is limited by the high viscosity impartedby silicas. When silica is used together with carbon black, the amountof silica can be decreased to as low as about 1 phr; as the amount ofsilica is decreased, lesser amounts of coupling agents and shieldingagents can be employed. Generally, the amounts of coupling agents andshielding agents range from about 4% to about 20% based on the weight ofsilica used.

A multitude of rubber curing agents (also called vulcanizing agents) maybe employed, including sulfur or peroxide-based curing systems. Curingagents are described in Kirk-Othmer, E NCYCLOPEDIA OF C HEMICAL TECHNOLOGY, Vol. 20, pgs. 365-468, (3^(rd) Ed. 1982), particularlyVulcanization Agents and Auxiliary Materials, pgs. 390-402, and A. Y.Coran, Vulcanization, E NCYCLOPEDIA OF P OLYMER S CIENCE AND ENGINEERING, (2^(nd) Ed. 1989), which are incorporated herein byreference. Vulcanizing agents may be used alone or in combination.

Other ingredients that are typically employed in rubber compounding mayalso be added to the rubber compositions. These include accelerators,accelerator activators, oils, plasticizer, waxes, scorch inhibitingagents, processing aids, zinc oxide, tackifying resins, reinforcingresins, fatty acids such as stearic acid, peptizers, and antidegradantssuch as antioxidants and antiozonants. In particular embodiments, theoils that are employed include those conventionally used as extenderoils, which are described above.

All ingredients of the rubber compositions can be mixed with standardmixing equipment such as Banbury or Brabender mixers, extruders,kneaders, and two-rolled mills. In one or more embodiments, theingredients are mixed in two or more stages. In the first stage (oftenreferred to as the masterbatch mixing stage), a so-called masterbatch,which typically includes the rubber component and filler, is prepared.To prevent premature vulcanization (also known as scorch), themasterbatch may exclude vulcanizing agents. The masterbatch may be mixedat a starting temperature of from about 25° C. to about 125° C. with adischarge temperature of about 135° C. to about 180° C. Once themasterbatch is prepared, the vulcanizing agents may be introduced andmixed into the masterbatch in a final mixing stage, which is typicallyconducted at relatively low temperatures so as to reduce the chances ofpremature vulcanization. Optionally, additional mixing stages, sometimescalled remills, can be employed between the masterbatch mixing stage andthe final mixing stage. One or more remill stages are often employedwhere the rubber composition includes silica as the filler. Variousingredients including the coupled polymers of this invention can beadded during these remills.

The mixing procedures and conditions particularly applicable tosilica-filled tire formulations are described in U.S. Pat. Nos.5,227,425, 5,719,207, and 5,717,022, as well as European Patent No.890,606, all of which are incorporated herein by reference. In oneembodiment, the initial masterbatch is prepared by including the coupledpolymers of this invention and silica in the substantial absence ofsilica coupling agents and silica shielding agents.

The rubber compositions prepared from the coupled polymers of thisinvention are particularly useful for forming tire components such astreads, subtreads, sidewalls, body ply skims, bead filler, and the like.Preferably, the coupled polymers of this invention are employed in treadand sidewall formulations. In one or more embodiments, these tread orsidewall formulations may include from about 10% to about 100% byweight, in other embodiments from about 35% to about 90% by weight, andin other embodiments from about 50% to about 80% by weight of thecoupled polymer based on the total weight of the rubber within theformulation.

Where the rubber compositions are employed in the manufacture of tires,these compositions can be processed into tire components according toordinary tire manufacturing techniques including standard rubbershaping, molding and curing techniques. Typically, vulcanization iseffected by heating the vulcanizable composition in a mold; e.g., it maybe heated to about 140° C. to about 180° C. Cured or crosslinked rubbercompositions may be referred to as vulcanizates, which generally containthree-dimensional polymeric networks that are thermoset. The otheringredients, such as fillers and processing aids, may be evenlydispersed throughout the crosslinked network. Pneumatic tires can bemade as discussed in U.S. Pat. Nos. 5,866,171, 5,876,527, 5,931,211, and5,971,046, which are incorporated herein by reference.

In order to demonstrate the practice of the present invention, thefollowing examples have been prepared and tested. The examples shouldnot, however, be viewed as limiting the scope of the invention. Theclaims will serve to define the invention.

EXAMPLES

Hexane, butadiene, and styrene were purified by distillation and driedusing a Lectrodryer prior to use. All other compounds were used aspurchased. The polymerization reactor consisted of a 25-gallon stainlesscylinder equipped with a mechanical agitator (shaft and blades) capableof mixing high viscosity polymer cement. The polymerization reactor wasequipped with a jacket containing water used to control the temperatureof the polymerization solution.

The Mooney viscosities (ML₁₊₄) of the polymer samples were determined at100° C. by using a Monsanto Mooney viscometer with a large rotor, aone-minute warm-up time, and a four-minute running time. The numberaverage (Mn) and weight average (Mw) molecular weights of the polymersamples were determined by gel permeation chromatography (GPC). Themicrostructure of the polymers was determined by ¹HNMR spectroscopyusing CDCl₃ as a solvent.

Several methods were used to measure cold flow resistance. First, usinga Scott Tester, a cylinder-shaped polymer sample with a diameter of 40mm and a height of 13.0 mm was placed on its cylindrical base and a 5000g mass was placed on top of the cylinder for 30 minutes at which timethe height of the cylinder was measure. Second, gravity cold flow testswere conducted by preparing a cylinder-shaped polymer sample with adiameter of 10 mm and a height of 12.5 mm. The cylinder was placed onits circular base and left in place for 28 days at which time the heightof the cylinder was measured. Third, to simulate storage of a stack ofpolymers on top of the polymer sample, the experiment was repeated witha weight equal to the weight of 7 polymer cylinders placed on thecylinder-shaped polymer sample for 28 days.

For compounding studies, the carbon black-filled formulations weresimilar to those conventionally employed for making tire treads. Therubber formulations were sheeted and cured according to conventionaltechniques. The Mooney viscosity (ML₁₊₄) of the uncured compound wasdetermined at 130° C. by using a Alpha Technologies Mooney viscometerwith a large rotor, a one-minute warm-up time, and a four minute runningtime. The tensile at break (Tb), and the elongation at break (Eb) weredetermined according to ASTM D412. The Payne effect data (ΔG′) andhysteresis data (tan δ) of the vulcanizates were obtained from a dynamicstrain sweep experiment, which was conducted at 50° C. and 15 Hz withstrain sweeping from 0.1% to 14.25%. ΔG′ is the difference between G′ at0.1% strain and G′ at 14.25% strain.

Bound rubber, a measure of the percentage of rubber bound, through someinteraction, to the filler, was determined by solvent extraction withtoluene at room temperature. More specifically, a test specimen of eachuncured rubber formulation was placed in toluene for three days. Thesolvent was removed and the residue was dried and weighed. Thepercentage of bound rubber was then determined according to the formula:% bound rubber=(100(W _(d) −F))/Rwhere W_(d) is the weight of the dried residue, F is the weight of thefiller and any other solvent insoluble matter in the original sample,and R is the weight of the rubber in the original sample.

The reactor was thoroughly purged with a steam of dry nitrogen, whichwas then replaced with 4.82 kg of hexane, 1.56 kg of a 34.0% styrene inhexane solution, and 4.94 kg of 21.2% butadiene in hexane solution.After the monomer solution was thermostated at 23° C., thepolymerization was initiated by charging 10.9 mL of 1.6 M n-butyllithium (BuLi) in hexane, 4.94 mL of 3.0 M hexamethyleneimine in hexane,1.31 mL of 1.6 M 2,2-di(2-tetrahydrofuryl)propane in hexane, and 0.96 mLof 1.0 M potassium 2-methyl-2-butanolate in hexane into the reactor. Thereactor was heated until the polymerization temperature reached 60° C.as which cooling water at a temperature of 32° C. was applied. When thepolymerization temperature reached 62° C., the temperature of thecooling water was lowered to 21° C. while the polymerization temperaturecontinued to rise to 89° C. Ten minutes after the peak exotherm wasachieved, the polymer cement was dropped into large, sealed bottles thathad been purged with nitrogen. The polymer cement was thenfunctionalized with tin tetrachloride or a combination oftolyl-2,4-diisocyanate and glycerol as set forth in Table 1.Specifically, polymer samples 1, 3, and 4, were treated with thediisocyanate and shaken vigorously for 5 minutes at 50° C. Then,glycerol was added to the polymer cement and the solution was shaken for30 minutes at 50° C. The amount of glycerol added after diisocyanateaddition was the minimum amount of hydroxyls needed to react with allremaining isocyanate functional groups. For polymer 2, the polymercement was treated with tin tetrachloride (SnCl₄) and was agitated for30 minutes at 50° C. After functionalization was complete in polymersamples 1, 2, 3, and 4, the polymer cement was treated with 3.0 mL of a0.5 M 2,6-di-tert-butyl-4-methylphenol (BHT) in isopropanol. Thepolymers were isolated from the cements by coagulation in BHT-saturatedisopropanol followed by solvent removal via drum drying. Table 1 alsoprovides the characteristics of each of the functionalized polymers.

TABLE 1 Polymer Sample 1 2 3 4 Tolyl-2,4-diisocyanate/Li 0/1 —   4/1  8/1 Glycerol/Li — — 2.3/1 5.0/1 SnCl₄/Li — 0.19/1 — — Base ML₁₊₄ 19.819.8 19.8 19.8 Coupled ML₁₊₄ — 84.0 46.7 55.8 Mn (×10³ g/mol) 112 190130 130 Mw (×10³ g/mol) 118 318 214 159 MWD 1.05 1.67 1.65 1.22 %Coupling — 58 23 22 % Total Styrene 25.8 25.8 25.8 25.8 % Block Styrene9.4 9.4 9.4 9.4 % Block Styrene_((Stv=100%)) 36.4 36.4 36.4 36.4 % 1,220.2 20.2 20.2 20.2 % 1,2_((butadiene=100%)) 27.2 27.2 27.2 27.2 % 1,454.0 54.0 54.0 54.0

The cold flow resistance of each polymer in Table 1 was measured and isreported in Table 2. Polymers 3 and 4, which were coupled withdiisocyanate and glycerol, were much more resistant to cold flow thanuncoupled Polymer 1 and had similar cold flow properties as Polymer 2,which was coupled with SnCl₄.

TABLE 2 Polymer Sample 1 2 3 4 Cold Flow - Scott Tester 5.4 11.4 9.2 9.8(39 kPa, 25° C., 30 min) Initial Height = 12.5 mm Cold Flow - Gravity4.5 13.1** 14.0** 13.2** (0 kPA, Room Temp., 28 days) Initial Height =12.5 mm Cold Flow - Gravity 0.6 11.2 8.6 11.2 (4 kPA, Room Temp., 28days) Initial Height = 12.5 mm **Polymer sample expanded once removedfrom the cylinder-shaped mold.

The polymer samples 1, 2, 3, and 4 were used to make cured rubbersamples using carbon black-filled rubber formulations as shown in Table3.

TABLE 3 parts per hundred rubber (phr) Master Batch Polymer 100 CarbonBlack 50 Oil 300 Stearic Acid 2 Wax Blend 2 Antioxidant 0.95 Final BatchMaster Batch 164.95 Sulfur and 2.8 Accelerators Zinc Oxide 2.5

Once compounded and cured, the physical properties of the rubber sampleswere evaluated and are shown in Table 4.

TABLE 4 Polymer Sample 1 2 3 4 160° C. Cure Rheometer t90% (min) 3.153.25 2.64 3.05 160° C. Cure Rheometer MH-ML (kg-cm) 15.79 14.09 14.9014.28 Compound ML₁₊₄ @ 130° C. 45.0 68.4 64.6 69.5 300% Modulus @ 23° C.(MPa) 14.137 15.378 15.767 15.269 Tensile Break Stress @ 23° C. (MPa)32.337 19.748 21.246 24.825 Elongation at Break @ 23° C. (%) 383.55306.56 300.13 330.11 tanδ [TS; 0° C.; 10 Hz, 2%] 0.282 0.263 0.264 0.268tanδ [SS; 60° C.; 10 Hz, 5%] 0.120 0.109 0.108 0.115 G′ (MPa) [SS; 50°C.; 15 Hz, 5%] 2.24 2.17 2.20 2.37 ΔG′ (MPa) [SS; 50° C.; 15 Hz,0.25%-14.25%] 0.59 0.59 0.56 0.77 Bound Rubber (%) 30.09 41.65 39.0642.93 *The amount of glycerol added after diisocyanate addition was theminimal amount needed to react with all remaining isocyanate functionalgroups.

Polymers 3 and 4, which were coupled with diisocyanates and glycerol,had similar compound Mooney (ML₁₊₄ @130° C.) as Polymer 2, which wascoupled with SnCl₄, and all polymers were readily processed duringmixing. When compared to Polymer 2, Polymers 3 and 4 have similar curetimes, modulus values, tensile break stresses, and elongation at breaks.The various methods used to measure hysteresis (tan δ) showed adesirable reduction in hysteresis when comparing Polymers 3 and 4against uncoupled Polymer 1. Likewise, this desirable reduction inhysteresis is similar to Polymer 2. In conclusion, polymers coupled withdiisocyanate and glycerol had similar compounded properties to polymerscoupled with tin-coupling reagents.

Various modifications and alterations that do not depart from the scopeand spirit of this invention will become apparent to those skilled inthe art. This invention is not to be duly limited to the illustrativeembodiments set forth herein.

What is claimed is:
 1. A method for preparing a coupled polymer havingadvantageous resistance to coldflow, the method comprising the steps of:(i) polymerizing conjugated diene monomer, and optionally monomercopolymerizable therewith, to form a reactive polymer within apolymerization mixture; (ii) adding a diisocyanate into thepolymerization mixture, thereby reacting the reactive polymer with thediisocyanate to form an intermediate polymer product; and (iii) afterthe diisocyanate has reacted with the reactive polymer adding a triolinto the polymerization mixture including the intermediate polymer,thereby reacting the intermediate polymer product with a triol to formthe coupled polymer product, where the coupled polymer product isdefined by the formula:

 where R¹⁰is a multivalent organic group deriving from the triol, R¹¹ isa divalent organic group deriving from the diisocyanate, and each R¹² isa residue of the reactive polymer; and  where the monomer is polymerizedwith a lanthanide-based catalyst or a organolithium initiator with amolar ratio of the isocyanate functionality of the diisocyanate to themoles of lithium cation in the organolithium initiator (—NCO/Li) fromabout 50:1 to about 1:1.
 2. The method of claim 1, where thediisocyanate is a diisocyanato hydrocarbyl selected from the groupconsisting of diisocyanatoalkyls, diisocyanatocycloalkyls,diisocyantoaryls, diisocyanatoalkenyls, and diisocyanatoalkynyls.
 3. Themethod of claim 1, where the diisocyanate is selected from the groupconsisting of methylene diphenyl diisocyanate, toluene diisocyanate,hexamethylene diisocyanate, isophorone diisocyanate, and4,4′-methylenebis (cyclohexyl isocyanate).
 4. The method of claim 1,where the triol is selected from the group consisting of alkyltriols,cycloalkyltriols, aryltriols, alkenyltriols, and alkynyltriols.
 5. Themethod of claim 1, where the triol is glycerol.
 6. The method of claim1, where said step of polymerizing monomer includes polymerizingconjugated diene monomer and monomer copolymerizable therewith.
 7. Themethod of claim 1, where said step of polymerizing takes place usinganionic polymerization techniques.
 8. The method of claim 1, where saidstep of polymerizing takes place using an organolithium initiator. 9.The method of claim 1, where said step of polymerizing takes place usinga lanthanide-based catalyst system.
 10. The method of claim 1, where themonomer is polymerized with an organolithium initiator and the molarratio of the isocyanate functionality to the moles of lithium cation(—NCO/Li) is from about 10:1 to about 1:1.
 11. The method of claim 1,where the monomer is polymerized with an organolithium initiator andmolar ratio of the isocyanate functionality to the moles of lithiumcation (—NCO/Li) is from about 5:1 to about 1:1.
 12. The method of claim1, where the monomer is polymerized with a lanthanide-based catalyst andthe molar ratio of the isocyanate functionality of the polyisocyanate tothe moles of lanthanide metal in the lanthanide-based catalyst (—NCO/Ln)is from about 1000:1 to about 1:1.
 13. The method of claim 1, where thecoupled polymer product includes two or more polydiene or polydienecopolymers coupled through a residue of the polyol.